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* bpf: add bpf_jit_limit knob to restrict unpriv allocationsDaniel Borkmann2019-08-251-3/+46
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit ede95a63b5e84ddeea6b0c473b36ab8bfd8c6ce3 upstream. Rick reported that the BPF JIT could potentially fill the entire module space with BPF programs from unprivileged users which would prevent later attempts to load normal kernel modules or privileged BPF programs, for example. If JIT was enabled but unsuccessful to generate the image, then before commit 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") we would always fall back to the BPF interpreter. Nowadays in the case where the CONFIG_BPF_JIT_ALWAYS_ON could be set, then the load will abort with a failure since the BPF interpreter was compiled out. Add a global limit and enforce it for unprivileged users such that in case of BPF interpreter compiled out we fail once the limit has been reached or we fall back to BPF interpreter earlier w/o using module mem if latter was compiled in. In a next step, fair share among unprivileged users can be resolved in particular for the case where we would fail hard once limit is reached. Fixes: 290af86629b2 ("bpf: introduce BPF_JIT_ALWAYS_ON config") Fixes: 0a14842f5a3c ("net: filter: Just In Time compiler for x86-64") Co-Developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: LKML <linux-kernel@vger.kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: get rid of pure_initcall dependency to enable jitsDaniel Borkmann2019-08-251-7/+12
| | | | | | | | | | | | | | | | | | | | | | commit fa9dd599b4dae841924b022768354cfde9affecb upstream. Having a pure_initcall() callback just to permanently enable BPF JITs under CONFIG_BPF_JIT_ALWAYS_ON is unnecessary and could leave a small race window in future where JIT is still disabled on boot. Since we know about the setting at compilation time anyway, just initialize it properly there. Also consolidate all the individual bpf_jit_enable variables into a single one and move them under one location. Moreover, don't allow for setting unspecified garbage values on them. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [bwh: Backported to 4.14 as dependency of commit 2e4a30983b0f "bpf: restrict access to core bpf sysctls": - Adjust context] Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: silence warning messages in coreValdis Klētnieks2019-07-311-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit aee450cbe482a8c2f6fa5b05b178ef8b8ff107ca ] Compiling kernel/bpf/core.c with W=1 causes a flood of warnings: kernel/bpf/core.c:1198:65: warning: initialized field overwritten [-Woverride-init] 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true | ^~~~ kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL' 1087 | INSN_3(ALU, ADD, X), \ | ^~~~~~ kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP' 1202 | BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL), | ^~~~~~~~~~~~ kernel/bpf/core.c:1198:65: note: (near initialization for 'public_insntable[12]') 1198 | #define BPF_INSN_3_TBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = true | ^~~~ kernel/bpf/core.c:1087:2: note: in expansion of macro 'BPF_INSN_3_TBL' 1087 | INSN_3(ALU, ADD, X), \ | ^~~~~~ kernel/bpf/core.c:1202:3: note: in expansion of macro 'BPF_INSN_MAP' 1202 | BPF_INSN_MAP(BPF_INSN_2_TBL, BPF_INSN_3_TBL), | ^~~~~~~~~~~~ 98 copies of the above. The attached patch silences the warnings, because we *know* we're overwriting the default initializer. That leaves bpf/core.c with only 6 other warnings, which become more visible in comparison. Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu> Acked-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
* bpf: devmap: fix use-after-free Read in __dev_map_entry_freeEric Dumazet2019-05-311-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 2baae3545327632167c0180e9ca1d467416f1919 upstream. synchronize_rcu() is fine when the rcu callbacks only need to free memory (kfree_rcu() or direct kfree() call rcu call backs) __dev_map_entry_free() is a bit more complex, so we need to make sure that call queued __dev_map_entry_free() callbacks have completed. sysbot report: BUG: KASAN: use-after-free in dev_map_flush_old kernel/bpf/devmap.c:365 [inline] BUG: KASAN: use-after-free in __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 Read of size 8 at addr ffff8801b8da38c8 by task ksoftirqd/1/18 CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 4.17.0+ #39 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 dev_map_flush_old kernel/bpf/devmap.c:365 [inline] __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 __rcu_reclaim kernel/rcu/rcu.h:178 [inline] rcu_do_batch kernel/rcu/tree.c:2558 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2818 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2785 [inline] rcu_process_callbacks+0xe9d/0x1760 kernel/rcu/tree.c:2802 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:284 run_ksoftirqd+0x86/0x100 kernel/softirq.c:645 smpboot_thread_fn+0x417/0x870 kernel/smpboot.c:164 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 Allocated by task 6675: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620 kmalloc include/linux/slab.h:513 [inline] kzalloc include/linux/slab.h:706 [inline] dev_map_alloc+0x208/0x7f0 kernel/bpf/devmap.c:102 find_and_alloc_map kernel/bpf/syscall.c:129 [inline] map_create+0x393/0x1010 kernel/bpf/syscall.c:453 __do_sys_bpf kernel/bpf/syscall.c:2351 [inline] __se_sys_bpf kernel/bpf/syscall.c:2328 [inline] __x64_sys_bpf+0x303/0x510 kernel/bpf/syscall.c:2328 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 26: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kfree+0xd9/0x260 mm/slab.c:3813 dev_map_free+0x4fa/0x670 kernel/bpf/devmap.c:191 bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:262 process_one_work+0xc64/0x1b70 kernel/workqueue.c:2153 worker_thread+0x181/0x13a0 kernel/workqueue.c:2296 kthread+0x345/0x410 kernel/kthread.c:240 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 The buggy address belongs to the object at ffff8801b8da37c0 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 264 bytes inside of 512-byte region [ffff8801b8da37c0, ffff8801b8da39c0) The buggy address belongs to the page: page:ffffea0006e368c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0xffff8801b8da3540 flags: 0x2fffc0000000100(slab) raw: 02fffc0000000100 ffffea0007217b88 ffffea0006e30cc8 ffff8801da800940 raw: ffff8801b8da3540 ffff8801b8da3040 0000000100000004 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801b8da3780: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff8801b8da3800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8801b8da3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801b8da3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b8da3980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc Fixes: 546ac1ffb70d ("bpf: add devmap, a map for storing net device references") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot+457d3e2ffbcf31aee5c0@syzkaller.appspotmail.com Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf, lru: avoid messing with eviction heuristics upon syscall lookupDaniel Borkmann2019-05-251-5/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 50b045a8c0ccf44f76640ac3eea8d80ca53979a3 upstream. One of the biggest issues we face right now with picking LRU map over regular hash table is that a map walk out of user space, for example, to just dump the existing entries or to remove certain ones, will completely mess up LRU eviction heuristics and wrong entries such as just created ones will get evicted instead. The reason for this is that we mark an entry as "in use" via bpf_lru_node_set_ref() from system call lookup side as well. Thus upon walk, all entries are being marked, so information of actual least recently used ones are "lost". In case of Cilium where it can be used (besides others) as a BPF based connection tracker, this current behavior causes disruption upon control plane changes that need to walk the map from user space to evict certain entries. Discussion result from bpfconf [0] was that we should simply just remove marking from system call side as no good use case could be found where it's actually needed there. Therefore this patch removes marking for regular LRU and per-CPU flavor. If there ever should be a need in future, the behavior could be selected via map creation flag, but due to mentioned reason we avoid this here. [0] http://vger.kernel.org/bpfconf.html Fixes: 29ba732acbee ("bpf: Add BPF_MAP_TYPE_LRU_HASH") Fixes: 8f8449384ec3 ("bpf: Add BPF_MAP_TYPE_LRU_PERCPU_HASH") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: add map_lookup_elem_sys_only for lookups from syscall sideDaniel Borkmann2019-05-251-1/+4
| | | | | | | | | | | | | | | | | | | | | commit c6110222c6f49ea68169f353565eb865488a8619 upstream. Add a callback map_lookup_elem_sys_only() that map implementations could use over map_lookup_elem() from system call side in case the map implementation needs to handle the latter differently than from the BPF data path. If map_lookup_elem_sys_only() is set, this will be preferred pick for map lookups out of user space. This hook is used in a follow-up fix for LRU map, but once development window opens, we can convert other map types from map_lookup_elem() (here, the one called upon BPF_MAP_LOOKUP_ELEM cmd is meant) over to use the callback to simplify and clean up the latter. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix sanitation rewrite in case of non-pointersDaniel Borkmann2019-04-201-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 3612af783cf52c74a031a2f11b82247b2599d3cd upstream. Marek reported that he saw an issue with the below snippet in that timing measurements where off when loaded as unpriv while results were reasonable when loaded as privileged: [...] uint64_t a = bpf_ktime_get_ns(); uint64_t b = bpf_ktime_get_ns(); uint64_t delta = b - a; if ((int64_t)delta > 0) { [...] Turns out there is a bug where a corner case is missing in the fix d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar type from different paths"), namely fixup_bpf_calls() only checks whether aux has a non-zero alu_state, but it also needs to test for the case of BPF_ALU_NON_POINTER since in both occasions we need to skip the masking rewrite (as there is nothing to mask). Fixes: d3bd7413e0ca ("bpf: fix sanitation of alu op with pointer / scalar type from different paths") Reported-by: Marek Majkowski <marek@cloudflare.com> Reported-by: Arthur Fabre <afabre@cloudflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/netdev/CAJPywTJqP34cK20iLM5YmUMz9KXQOdu1-+BZrGMAGgLuBWz7fg@mail.gmail.com/T/ Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: do not restore dst_reg when cur_state is freedXu Yu2019-04-201-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 0803278b0b4d8eeb2b461fb698785df65a725d9e upstream. Syzkaller hit 'KASAN: use-after-free Write in sanitize_ptr_alu' bug. Call trace: dump_stack+0xbf/0x12e print_address_description+0x6a/0x280 kasan_report+0x237/0x360 sanitize_ptr_alu+0x85a/0x8d0 adjust_ptr_min_max_vals+0x8f2/0x1ca0 adjust_reg_min_max_vals+0x8ed/0x22e0 do_check+0x1ca6/0x5d00 bpf_check+0x9ca/0x2570 bpf_prog_load+0xc91/0x1030 __se_sys_bpf+0x61e/0x1f00 do_syscall_64+0xc8/0x550 entry_SYSCALL_64_after_hwframe+0x49/0xbe Fault injection trace:  kfree+0xea/0x290  free_func_state+0x4a/0x60  free_verifier_state+0x61/0xe0  push_stack+0x216/0x2f0 <- inject failslab  sanitize_ptr_alu+0x2b1/0x8d0  adjust_ptr_min_max_vals+0x8f2/0x1ca0  adjust_reg_min_max_vals+0x8ed/0x22e0  do_check+0x1ca6/0x5d00  bpf_check+0x9ca/0x2570  bpf_prog_load+0xc91/0x1030  __se_sys_bpf+0x61e/0x1f00  do_syscall_64+0xc8/0x550  entry_SYSCALL_64_after_hwframe+0x49/0xbe When kzalloc() fails in push_stack(), free_verifier_state() will free current verifier state. As push_stack() returns, dst_reg was restored if ptr_is_dst_reg is false. However, as member of the cur_state, dst_reg is also freed, and error occurs when dereferencing dst_reg. Simply fix it by testing ret of push_stack() before restoring dst_reg. Fixes: 979d63d50c0c ("bpf: prevent out of bounds speculation on pointer arithmetic") Signed-off-by: Xu Yu <xuyu@linux.alibaba.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix inner map masking to prevent oob under speculationDaniel Borkmann2019-04-201-2/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 9d5564ddcf2a0f5ba3fa1c3a1f8a1b59ad309553 upstream. During review I noticed that inner meta map setup for map in map is buggy in that it does not propagate all needed data from the reference map which the verifier is later accessing. In particular one such case is index masking to prevent out of bounds access under speculative execution due to missing the map's unpriv_array/index_mask field propagation. Fix this such that the verifier is generating the correct code for inlined lookups in case of unpriviledged use. Before patch (test_verifier's 'map in map access' dump): # bpftool prog dump xla id 3 0: (62) *(u32 *)(r10 -4) = 0 1: (bf) r2 = r10 2: (07) r2 += -4 3: (18) r1 = map[id:4] 5: (07) r1 += 272 | 6: (61) r0 = *(u32 *)(r2 +0) | 7: (35) if r0 >= 0x1 goto pc+6 | Inlined map in map lookup 8: (54) (u32) r0 &= (u32) 0 | with index masking for 9: (67) r0 <<= 3 | map->unpriv_array. 10: (0f) r0 += r1 | 11: (79) r0 = *(u64 *)(r0 +0) | 12: (15) if r0 == 0x0 goto pc+1 | 13: (05) goto pc+1 | 14: (b7) r0 = 0 | 15: (15) if r0 == 0x0 goto pc+11 16: (62) *(u32 *)(r10 -4) = 0 17: (bf) r2 = r10 18: (07) r2 += -4 19: (bf) r1 = r0 20: (07) r1 += 272 | 21: (61) r0 = *(u32 *)(r2 +0) | Index masking missing (!) 22: (35) if r0 >= 0x1 goto pc+3 | for inner map despite 23: (67) r0 <<= 3 | map->unpriv_array set. 24: (0f) r0 += r1 | 25: (05) goto pc+1 | 26: (b7) r0 = 0 | 27: (b7) r0 = 0 28: (95) exit After patch: # bpftool prog dump xla id 1 0: (62) *(u32 *)(r10 -4) = 0 1: (bf) r2 = r10 2: (07) r2 += -4 3: (18) r1 = map[id:2] 5: (07) r1 += 272 | 6: (61) r0 = *(u32 *)(r2 +0) | 7: (35) if r0 >= 0x1 goto pc+6 | Same inlined map in map lookup 8: (54) (u32) r0 &= (u32) 0 | with index masking due to 9: (67) r0 <<= 3 | map->unpriv_array. 10: (0f) r0 += r1 | 11: (79) r0 = *(u64 *)(r0 +0) | 12: (15) if r0 == 0x0 goto pc+1 | 13: (05) goto pc+1 | 14: (b7) r0 = 0 | 15: (15) if r0 == 0x0 goto pc+12 16: (62) *(u32 *)(r10 -4) = 0 17: (bf) r2 = r10 18: (07) r2 += -4 19: (bf) r1 = r0 20: (07) r1 += 272 | 21: (61) r0 = *(u32 *)(r2 +0) | 22: (35) if r0 >= 0x1 goto pc+4 | Now fixed inlined inner map 23: (54) (u32) r0 &= (u32) 0 | lookup with proper index masking 24: (67) r0 <<= 3 | for map->unpriv_array. 25: (0f) r0 += r1 | 26: (05) goto pc+1 | 27: (b7) r0 = 0 | 28: (b7) r0 = 0 29: (95) exit Fixes: b2157399cc98 ("bpf: prevent out-of-bounds speculation") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Vallish Vaidyeshwara <vallish@amazon.com> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix sanitation of alu op with pointer / scalar type from different pathsDaniel Borkmann2019-04-201-13/+48
| | | | | | | | | | | | | | | | | | | | | | commit d3bd7413e0ca40b60cf60d4003246d067cafdeda upstream. While 979d63d50c0c ("bpf: prevent out of bounds speculation on pointer arithmetic") took care of rejecting alu op on pointer when e.g. pointer came from two different map values with different map properties such as value size, Jann reported that a case was not covered yet when a given alu op is used in both "ptr_reg += reg" and "numeric_reg += reg" from different branches where we would incorrectly try to sanitize based on the pointer's limit. Catch this corner case and reject the program instead. Fixes: 979d63d50c0c ("bpf: prevent out of bounds speculation on pointer arithmetic") Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Vallish Vaidyeshwara <vallish@amazon.com> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: prevent out of bounds speculation on pointer arithmeticDaniel Borkmann2019-04-201-6/+178
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 979d63d50c0c0f7bc537bf821e056cc9fe5abd38 upstream. Jann reported that the original commit back in b2157399cc98 ("bpf: prevent out-of-bounds speculation") was not sufficient to stop CPU from speculating out of bounds memory access: While b2157399cc98 only focussed on masking array map access for unprivileged users for tail calls and data access such that the user provided index gets sanitized from BPF program and syscall side, there is still a more generic form affected from BPF programs that applies to most maps that hold user data in relation to dynamic map access when dealing with unknown scalars or "slow" known scalars as access offset, for example: - Load a map value pointer into R6 - Load an index into R7 - Do a slow computation (e.g. with a memory dependency) that loads a limit into R8 (e.g. load the limit from a map for high latency, then mask it to make the verifier happy) - Exit if R7 >= R8 (mispredicted branch) - Load R0 = R6[R7] - Load R0 = R6[R0] For unknown scalars there are two options in the BPF verifier where we could derive knowledge from in order to guarantee safe access to the memory: i) While </>/<=/>= variants won't allow to derive any lower or upper bounds from the unknown scalar where it would be safe to add it to the map value pointer, it is possible through ==/!= test however. ii) another option is to transform the unknown scalar into a known scalar, for example, through ALU ops combination such as R &= <imm> followed by R |= <imm> or any similar combination where the original information from the unknown scalar would be destroyed entirely leaving R with a constant. The initial slow load still precedes the latter ALU ops on that register, so the CPU executes speculatively from that point. Once we have the known scalar, any compare operation would work then. A third option only involving registers with known scalars could be crafted as described in [0] where a CPU port (e.g. Slow Int unit) would be filled with many dependent computations such that the subsequent condition depending on its outcome has to wait for evaluation on its execution port and thereby executing speculatively if the speculated code can be scheduled on a different execution port, or any other form of mistraining as described in [1], for example. Given this is not limited to only unknown scalars, not only map but also stack access is affected since both is accessible for unprivileged users and could potentially be used for out of bounds access under speculation. In order to prevent any of these cases, the verifier is now sanitizing pointer arithmetic on the offset such that any out of bounds speculation would be masked in a way where the pointer arithmetic result in the destination register will stay unchanged, meaning offset masked into zero similar as in array_index_nospec() case. With regards to implementation, there are three options that were considered: i) new insn for sanitation, ii) push/pop insn and sanitation as inlined BPF, iii) reuse of ax register and sanitation as inlined BPF. Option i) has the downside that we end up using from reserved bits in the opcode space, but also that we would require each JIT to emit masking as native arch opcodes meaning mitigation would have slow adoption till everyone implements it eventually which is counter-productive. Option ii) and iii) have both in common that a temporary register is needed in order to implement the sanitation as inlined BPF since we are not allowed to modify the source register. While a push / pop insn in ii) would be useful to have in any case, it requires once again that every JIT needs to implement it first. While possible, amount of changes needed would also be unsuitable for a -stable patch. Therefore, the path which has fewer changes, less BPF instructions for the mitigation and does not require anything to be changed in the JITs is option iii) which this work is pursuing. The ax register is already mapped to a register in all JITs (modulo arm32 where it's mapped to stack as various other BPF registers there) and used in constant blinding for JITs-only so far. It can be reused for verifier rewrites under certain constraints. The interpreter's tmp "register" has therefore been remapped into extending the register set with hidden ax register and reusing that for a number of instructions that needed the prior temporary variable internally (e.g. div, mod). This allows for zero increase in stack space usage in the interpreter, and enables (restricted) generic use in rewrites otherwise as long as such a patchlet does not make use of these instructions. The sanitation mask is dynamic and relative to the offset the map value or stack pointer currently holds. There are various cases that need to be taken under consideration for the masking, e.g. such operation could look as follows: ptr += val or val += ptr or ptr -= val. Thus, the value to be sanitized could reside either in source or in destination register, and the limit is different depending on whether the ALU op is addition or subtraction and depending on the current known and bounded offset. The limit is derived as follows: limit := max_value_size - (smin_value + off). For subtraction: limit := umax_value + off. This holds because we do not allow any pointer arithmetic that would temporarily go out of bounds or would have an unknown value with mixed signed bounds where it is unclear at verification time whether the actual runtime value would be either negative or positive. For example, we have a derived map pointer value with constant offset and bounded one, so limit based on smin_value works because the verifier requires that statically analyzed arithmetic on the pointer must be in bounds, and thus it checks if resulting smin_value + off and umax_value + off is still within map value bounds at time of arithmetic in addition to time of access. Similarly, for the case of stack access we derive the limit as follows: MAX_BPF_STACK + off for subtraction and -off for the case of addition where off := ptr_reg->off + ptr_reg->var_off.value. Subtraction is a special case for the masking which can be in form of ptr += -val, ptr -= -val, or ptr -= val. In the first two cases where we know that the value is negative, we need to temporarily negate the value in order to do the sanitation on a positive value where we later swap the ALU op, and restore original source register if the value was in source. The sanitation of pointer arithmetic alone is still not fully sufficient as is, since a scenario like the following could happen ... PTR += 0x1000 (e.g. K-based imm) PTR -= BIG_NUMBER_WITH_SLOW_COMPARISON PTR += 0x1000 PTR -= BIG_NUMBER_WITH_SLOW_COMPARISON [...] ... which under speculation could end up as ... PTR += 0x1000 PTR -= 0 [ truncated by mitigation ] PTR += 0x1000 PTR -= 0 [ truncated by mitigation ] [...] ... and therefore still access out of bounds. To prevent such case, the verifier is also analyzing safety for potential out of bounds access under speculative execution. Meaning, it is also simulating pointer access under truncation. We therefore "branch off" and push the current verification state after the ALU operation with known 0 to the verification stack for later analysis. Given the current path analysis succeeded it is likely that the one under speculation can be pruned. In any case, it is also subject to existing complexity limits and therefore anything beyond this point will be rejected. In terms of pruning, it needs to be ensured that the verification state from speculative execution simulation must never prune a non-speculative execution path, therefore, we mark verifier state accordingly at the time of push_stack(). If verifier detects out of bounds access under speculative execution from one of the possible paths that includes a truncation, it will reject such program. Given we mask every reg-based pointer arithmetic for unprivileged programs, we've been looking into how it could affect real-world programs in terms of size increase. As the majority of programs are targeted for privileged-only use case, we've unconditionally enabled masking (with its alu restrictions on top of it) for privileged programs for the sake of testing in order to check i) whether they get rejected in its current form, and ii) by how much the number of instructions and size will increase. We've tested this by using Katran, Cilium and test_l4lb from the kernel selftests. For Katran we've evaluated balancer_kern.o, Cilium bpf_lxc.o and an older test object bpf_lxc_opt_-DUNKNOWN.o and l4lb we've used test_l4lb.o as well as test_l4lb_noinline.o. We found that none of the programs got rejected by the verifier with this change, and that impact is rather minimal to none. balancer_kern.o had 13,904 bytes (1,738 insns) xlated and 7,797 bytes JITed before and after the change. Most complex program in bpf_lxc.o had 30,544 bytes (3,817 insns) xlated and 18,538 bytes JITed before and after and none of the other tail call programs in bpf_lxc.o had any changes either. For the older bpf_lxc_opt_-DUNKNOWN.o object we found a small increase from 20,616 bytes (2,576 insns) and 12,536 bytes JITed before to 20,664 bytes (2,582 insns) and 12,558 bytes JITed after the change. Other programs from that object file had similar small increase. Both test_l4lb.o had no change and remained at 6,544 bytes (817 insns) xlated and 3,401 bytes JITed and for test_l4lb_noinline.o constant at 5,080 bytes (634 insns) xlated and 3,313 bytes JITed. This can be explained in that LLVM typically optimizes stack based pointer arithmetic by using K-based operations and that use of dynamic map access is not overly frequent. However, in future we may decide to optimize the algorithm further under known guarantees from branch and value speculation. Latter seems also unclear in terms of prediction heuristics that today's CPUs apply as well as whether there could be collisions in e.g. the predictor's Value History/Pattern Table for triggering out of bounds access, thus masking is performed unconditionally at this point but could be subject to relaxation later on. We were generally also brainstorming various other approaches for mitigation, but the blocker was always lack of available registers at runtime and/or overhead for runtime tracking of limits belonging to a specific pointer. Thus, we found this to be minimally intrusive under given constraints. With that in place, a simple example with sanitized access on unprivileged load at post-verification time looks as follows: # bpftool prog dump xlated id 282 [...] 28: (79) r1 = *(u64 *)(r7 +0) 29: (79) r2 = *(u64 *)(r7 +8) 30: (57) r1 &= 15 31: (79) r3 = *(u64 *)(r0 +4608) 32: (57) r3 &= 1 33: (47) r3 |= 1 34: (2d) if r2 > r3 goto pc+19 35: (b4) (u32) r11 = (u32) 20479 | 36: (1f) r11 -= r2 | Dynamic sanitation for pointer 37: (4f) r11 |= r2 | arithmetic with registers 38: (87) r11 = -r11 | containing bounded or known 39: (c7) r11 s>>= 63 | scalars in order to prevent 40: (5f) r11 &= r2 | out of bounds speculation. 41: (0f) r4 += r11 | 42: (71) r4 = *(u8 *)(r4 +0) 43: (6f) r4 <<= r1 [...] For the case where the scalar sits in the destination register as opposed to the source register, the following code is emitted for the above example: [...] 16: (b4) (u32) r11 = (u32) 20479 17: (1f) r11 -= r2 18: (4f) r11 |= r2 19: (87) r11 = -r11 20: (c7) r11 s>>= 63 21: (5f) r2 &= r11 22: (0f) r2 += r0 23: (61) r0 = *(u32 *)(r2 +0) [...] JIT blinding example with non-conflicting use of r10: [...] d5: je 0x0000000000000106 _ d7: mov 0x0(%rax),%edi | da: mov $0xf153246,%r10d | Index load from map value and e0: xor $0xf153259,%r10 | (const blinded) mask with 0x1f. e7: and %r10,%rdi |_ ea: mov $0x2f,%r10d | f0: sub %rdi,%r10 | Sanitized addition. Both use r10 f3: or %rdi,%r10 | but do not interfere with each f6: neg %r10 | other. (Neither do these instructions f9: sar $0x3f,%r10 | interfere with the use of ax as temp fd: and %r10,%rdi | in interpreter.) 100: add %rax,%rdi |_ 103: mov 0x0(%rdi),%eax [...] Tested that it fixes Jann's reproducer, and also checked that test_verifier and test_progs suite with interpreter, JIT and JIT with hardening enabled on x86-64 and arm64 runs successfully. [0] Speculose: Analyzing the Security Implications of Speculative Execution in CPUs, Giorgi Maisuradze and Christian Rossow, https://arxiv.org/pdf/1801.04084.pdf [1] A Systematic Evaluation of Transient Execution Attacks and Defenses, Claudio Canella, Jo Van Bulck, Michael Schwarz, Moritz Lipp, Benjamin von Berg, Philipp Ortner, Frank Piessens, Dmitry Evtyushkin, Daniel Gruss, https://arxiv.org/pdf/1811.05441.pdf Fixes: b2157399cc98 ("bpf: prevent out-of-bounds speculation") Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Vallish Vaidyeshwara <vallish@amazon.com> [some checkpatch cleanups and backported to 4.14 by sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix check_map_access smin_value test when pointer contains offsetDaniel Borkmann2019-04-201-1/+5
| | | | | | | | | | | | | | | | | | | | | | commit b7137c4eab85c1cf3d46acdde90ce1163b28c873 upstream. In check_map_access() we probe actual bounds through __check_map_access() with offset of reg->smin_value + off for lower bound and offset of reg->umax_value + off for the upper bound. However, even though the reg->smin_value could have a negative value, the final result of the sum with off could be positive when pointer arithmetic with known and unknown scalars is combined. In this case we reject the program with an error such as "R<x> min value is negative, either use unsigned index or do a if (index >=0) check." even though the access itself would be fine. Therefore extend the check to probe whether the actual resulting reg->smin_value + off is less than zero. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: restrict unknown scalars of mixed signed bounds for unprivilegedDaniel Borkmann2019-04-201-1/+8
| | | | | | | | | | | | | | | | | | | commit 9d7eceede769f90b66cfa06ad5b357140d5141ed upstream. For unknown scalars of mixed signed bounds, meaning their smin_value is negative and their smax_value is positive, we need to reject arithmetic with pointer to map value. For unprivileged the goal is to mask every map pointer arithmetic and this cannot reliably be done when it is unknown at verification time whether the scalar value is negative or positive. Given this is a corner case, the likelihood of breaking should be very small. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: restrict stack pointer arithmetic for unprivilegedDaniel Borkmann2019-04-201-21/+41
| | | | | | | | | | | | | | | | | | | | commit e4298d25830a866cc0f427d4bccb858e76715859 upstream. Restrict stack pointer arithmetic for unprivileged users in that arithmetic itself must not go out of bounds as opposed to the actual access later on. Therefore after each adjust_ptr_min_max_vals() with a stack pointer as a destination we simulate a check_stack_access() of 1 byte on the destination and once that fails the program is rejected for unprivileged program loads. This is analog to map value pointer arithmetic and needed for masking later on. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: restrict map value pointer arithmetic for unprivilegedDaniel Borkmann2019-04-201-0/+11
| | | | | | | | | | | | | | | | | | | commit 0d6303db7970e6f56ae700fa07e11eb510cda125 upstream. Restrict map value pointer arithmetic for unprivileged users in that arithmetic itself must not go out of bounds as opposed to the actual access later on. Therefore after each adjust_ptr_min_max_vals() with a map value pointer as a destination it will simulate a check_map_access() of 1 byte on the destination and once that fails the program is rejected for unprivileged program loads. We use this later on for masking any pointer arithmetic with the remainder of the map value space. The likelihood of breaking any existing real-world unprivileged eBPF program is very small for this corner case. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: enable access to ax register also from verifier rewriteDaniel Borkmann2019-04-201-0/+20
| | | | | | | | | | | | | | | | | | | | | commit 9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30 upstream. Right now we are using BPF ax register in JIT for constant blinding as well as in interpreter as temporary variable. Verifier will not be able to use it simply because its use will get overridden from the former in bpf_jit_blind_insn(). However, it can be made to work in that blinding will be skipped if there is prior use in either source or destination register on the instruction. Taking constraints of ax into account, the verifier is then open to use it in rewrites under some constraints. Note, ax register already has mappings in every eBPF JIT. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: move tmp variable into ax register in interpreterDaniel Borkmann2019-04-201-15/+16
| | | | | | | | | | | | | | | | | | commit 144cd91c4c2bced6eb8a7e25e590f6618a11e854 upstream. This change moves the on-stack 64 bit tmp variable in ___bpf_prog_run() into the hidden ax register. The latter is currently only used in JITs for constant blinding as a temporary scratch register, meaning the BPF interpreter will never see the use of ax. Therefore it is safe to use it for the cases where tmp has been used earlier. This is needed to later on allow restricted hidden use of ax in both interpreter and JITs. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: move {prev_,}insn_idx into verifier envDaniel Borkmann2019-04-201-33/+31
| | | | | | | | | | | | | | | | | | | commit c08435ec7f2bc8f4109401f696fd55159b4b40cb upstream. Move prev_insn_idx and insn_idx from the do_check() function into the verifier environment, so they can be read inside the various helper functions for handling the instructions. It's easier to put this into the environment rather than changing all call-sites only to pass it along. insn_idx is useful in particular since this later on allows to hold state in env->insn_aux_data[env->insn_idx]. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Vallish Vaidyeshwara <vallish@amazon.com> [Backported to 4.14 by sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix stack state printing in verifier logAlexei Starovoitov2019-04-201-1/+1
| | | | | | | | | | | | | | commit 12a3cc8424fe1237aaeb982dec4f0914ddd22f3e upstream. fix incorrect stack state prints in print_verifier_state() Fixes: 638f5b90d460 ("bpf: reduce verifier memory consumption") Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix verifier NULL pointer dereferenceCraig Gallek2019-04-201-4/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 8c01c4f896aa3404af948880dcb29a2d51c833dc upstream. do_check() can fail early without allocating env->cur_state under memory pressure. Syzkaller found the stack below on the linux-next tree because of this. kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 27062 Comm: syz-executor5 Not tainted 4.14.0-rc7+ #106 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801c2c74700 task.stack: ffff8801c3e28000 RIP: 0010:free_verifier_state kernel/bpf/verifier.c:347 [inline] RIP: 0010:bpf_check+0xcf4/0x19c0 kernel/bpf/verifier.c:4533 RSP: 0018:ffff8801c3e2f5c8 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 00000000fffffff4 RCX: 0000000000000000 RDX: 0000000000000070 RSI: ffffffff817d5aa9 RDI: 0000000000000380 RBP: ffff8801c3e2f668 R08: 0000000000000000 R09: 1ffff100387c5d9f R10: 00000000218c4e80 R11: ffffffff85b34380 R12: ffff8801c4dc6a28 R13: 0000000000000000 R14: ffff8801c4dc6a00 R15: ffff8801c4dc6a20 FS: 00007f311079b700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004d4a24 CR3: 00000001cbcd0000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: bpf_prog_load+0xcbb/0x18e0 kernel/bpf/syscall.c:1166 SYSC_bpf kernel/bpf/syscall.c:1690 [inline] SyS_bpf+0xae9/0x4620 kernel/bpf/syscall.c:1652 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x452869 RSP: 002b:00007f311079abe8 EFLAGS: 00000212 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452869 RDX: 0000000000000030 RSI: 0000000020168000 RDI: 0000000000000005 RBP: 00007f311079aa20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000004b7550 R13: 00007f311079ab58 R14: 00000000004b7560 R15: 0000000000000000 Code: df 48 c1 ea 03 80 3c 02 00 0f 85 e6 0b 00 00 4d 8b 6e 20 48 b8 00 00 00 00 00 fc ff df 49 8d bd 80 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 b6 0b 00 00 49 8b bd 80 03 00 00 e8 d6 0c 26 RIP: free_verifier_state kernel/bpf/verifier.c:347 [inline] RSP: ffff8801c3e2f5c8 RIP: bpf_check+0xcf4/0x19c0 kernel/bpf/verifier.c:4533 RSP: ffff8801c3e2f5c8 ---[ end trace c8d37f339dc64004 ]--- Fixes: 638f5b90d460 ("bpf: reduce verifier memory consumption") Fixes: 1969db47f8d0 ("bpf: fix verifier memory leaks") Signed-off-by: Craig Gallek <kraig@google.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix verifier memory leaksAlexei Starovoitov2019-04-201-9/+18
| | | | | | | | | | | | commit 1969db47f8d0e800397abd4ee4e8d27d2b578587 upstream. fix verifier memory leaks Fixes: 638f5b90d460 ("bpf: reduce verifier memory consumption") Signed-off-by: Alexei Starovoitov <ast@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: reduce verifier memory consumptionAlexei Starovoitov2019-04-201-147/+286
| | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 638f5b90d46016372a8e3e0a434f199cc5e12b8c upstream. the verifier got progressively smarter over time and size of its internal state grew as well. Time to reduce the memory consumption. Before: sizeof(struct bpf_verifier_state) = 6520 After: sizeof(struct bpf_verifier_state) = 896 It's done by observing that majority of BPF programs use little to no stack whereas verifier kept all of 512 stack slots ready always. Instead dynamically reallocate struct verifier state when stack access is detected. Runtime difference before vs after is within a noise. The number of processed instructions stays the same. Cc: jakub.kicinski@netronome.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net> [Backported to 4.14 by sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix use after free in bpf_evict_inodeDaniel Borkmann2019-04-201-14/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 1da6c4d9140cb7c13e87667dc4e1488d6c8fc10f ] syzkaller was able to generate the following UAF in bpf: BUG: KASAN: use-after-free in lookup_last fs/namei.c:2269 [inline] BUG: KASAN: use-after-free in path_lookupat.isra.43+0x9f8/0xc00 fs/namei.c:2318 Read of size 1 at addr ffff8801c4865c47 by task syz-executor2/9423 CPU: 0 PID: 9423 Comm: syz-executor2 Not tainted 4.20.0-rc1-next-20181109+ #110 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 lookup_last fs/namei.c:2269 [inline] path_lookupat.isra.43+0x9f8/0xc00 fs/namei.c:2318 filename_lookup+0x26a/0x520 fs/namei.c:2348 user_path_at_empty+0x40/0x50 fs/namei.c:2608 user_path include/linux/namei.h:62 [inline] do_mount+0x180/0x1ff0 fs/namespace.c:2980 ksys_mount+0x12d/0x140 fs/namespace.c:3258 __do_sys_mount fs/namespace.c:3272 [inline] __se_sys_mount fs/namespace.c:3269 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3269 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457569 Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fde6ed96c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457569 RDX: 0000000020000040 RSI: 0000000020000000 RDI: 0000000000000000 RBP: 000000000072bf00 R08: 0000000020000340 R09: 0000000000000000 R10: 0000000000200000 R11: 0000000000000246 R12: 00007fde6ed976d4 R13: 00000000004c2c24 R14: 00000000004d4990 R15: 00000000ffffffff Allocated by task 9424: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 __do_kmalloc mm/slab.c:3722 [inline] __kmalloc_track_caller+0x157/0x760 mm/slab.c:3737 kstrdup+0x39/0x70 mm/util.c:49 bpf_symlink+0x26/0x140 kernel/bpf/inode.c:356 vfs_symlink+0x37a/0x5d0 fs/namei.c:4127 do_symlinkat+0x242/0x2d0 fs/namei.c:4154 __do_sys_symlink fs/namei.c:4173 [inline] __se_sys_symlink fs/namei.c:4171 [inline] __x64_sys_symlink+0x59/0x80 fs/namei.c:4171 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 9425: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kfree+0xcf/0x230 mm/slab.c:3817 bpf_evict_inode+0x11f/0x150 kernel/bpf/inode.c:565 evict+0x4b9/0x980 fs/inode.c:558 iput_final fs/inode.c:1550 [inline] iput+0x674/0xa90 fs/inode.c:1576 do_unlinkat+0x733/0xa30 fs/namei.c:4069 __do_sys_unlink fs/namei.c:4110 [inline] __se_sys_unlink fs/namei.c:4108 [inline] __x64_sys_unlink+0x42/0x50 fs/namei.c:4108 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe In this scenario path lookup under RCU is racing with the final unlink in case of symlinks. As Linus puts it in his analysis: [...] We actually RCU-delay the inode freeing itself, but when we do the final iput(), the "evict()" function is called synchronously. Now, the simple fix would seem to just RCU-delay the kfree() of the symlink data in bpf_evict_inode(). Maybe that's the right thing to do. [...] Al suggested to piggy-back on the ->destroy_inode() callback in order to implement RCU deferral there which can then kfree() the inode->i_link eventually right before putting inode back into inode cache. By reusing free_inode_nonrcu() from there we can avoid the need for our own inode cache and just reuse generic one as we currently do. And in-fact on top of all this we should just get rid of the bpf_evict_inode() entirely. This means truncate_inode_pages_final() and clear_inode() will then simply be called by the fs core via evict(). Dropping the reference should really only be done when inode is unhashed and nothing reachable anymore, so it's better also moved into the final ->destroy_inode() callback. Fixes: 0f98621bef5d ("bpf, inode: add support for symlinks and fix mtime/ctime") Reported-by: syzbot+fb731ca573367b7f6564@syzkaller.appspotmail.com Reported-by: syzbot+a13e5ead792d6df37818@syzkaller.appspotmail.com Reported-by: syzbot+7a8ba368b47fdefca61e@syzkaller.appspotmail.com Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Analyzed-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Link: https://lore.kernel.org/lkml/0000000000006946d2057bbd0eef@google.com/T/ Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
* bpf: fix lockdep false positive in percpu_freelistAlexei Starovoitov2019-03-133-14/+35
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit a89fac57b5d080771efd4d71feaae19877cf68f0 ] Lockdep warns about false positive: [ 12.492084] 00000000e6b28347 (&head->lock){+...}, at: pcpu_freelist_push+0x2a/0x40 [ 12.492696] but this lock was taken by another, HARDIRQ-safe lock in the past: [ 12.493275] (&rq->lock){-.-.} [ 12.493276] [ 12.493276] [ 12.493276] and interrupts could create inverse lock ordering between them. [ 12.493276] [ 12.494435] [ 12.494435] other info that might help us debug this: [ 12.494979] Possible interrupt unsafe locking scenario: [ 12.494979] [ 12.495518] CPU0 CPU1 [ 12.495879] ---- ---- [ 12.496243] lock(&head->lock); [ 12.496502] local_irq_disable(); [ 12.496969] lock(&rq->lock); [ 12.497431] lock(&head->lock); [ 12.497890] <Interrupt> [ 12.498104] lock(&rq->lock); [ 12.498368] [ 12.498368] *** DEADLOCK *** [ 12.498368] [ 12.498837] 1 lock held by dd/276: [ 12.499110] #0: 00000000c58cb2ee (rcu_read_lock){....}, at: trace_call_bpf+0x5e/0x240 [ 12.499747] [ 12.499747] the shortest dependencies between 2nd lock and 1st lock: [ 12.500389] -> (&rq->lock){-.-.} { [ 12.500669] IN-HARDIRQ-W at: [ 12.500934] _raw_spin_lock+0x2f/0x40 [ 12.501373] scheduler_tick+0x4c/0xf0 [ 12.501812] update_process_times+0x40/0x50 [ 12.502294] tick_periodic+0x27/0xb0 [ 12.502723] tick_handle_periodic+0x1f/0x60 [ 12.503203] timer_interrupt+0x11/0x20 [ 12.503651] __handle_irq_event_percpu+0x43/0x2c0 [ 12.504167] handle_irq_event_percpu+0x20/0x50 [ 12.504674] handle_irq_event+0x37/0x60 [ 12.505139] handle_level_irq+0xa7/0x120 [ 12.505601] handle_irq+0xa1/0x150 [ 12.506018] do_IRQ+0x77/0x140 [ 12.506411] ret_from_intr+0x0/0x1d [ 12.506834] _raw_spin_unlock_irqrestore+0x53/0x60 [ 12.507362] __setup_irq+0x481/0x730 [ 12.507789] setup_irq+0x49/0x80 [ 12.508195] hpet_time_init+0x21/0x32 [ 12.508644] x86_late_time_init+0xb/0x16 [ 12.509106] start_kernel+0x390/0x42a [ 12.509554] secondary_startup_64+0xa4/0xb0 [ 12.510034] IN-SOFTIRQ-W at: [ 12.510305] _raw_spin_lock+0x2f/0x40 [ 12.510772] try_to_wake_up+0x1c7/0x4e0 [ 12.511220] swake_up_locked+0x20/0x40 [ 12.511657] swake_up_one+0x1a/0x30 [ 12.512070] rcu_process_callbacks+0xc5/0x650 [ 12.512553] __do_softirq+0xe6/0x47b [ 12.512978] irq_exit+0xc3/0xd0 [ 12.513372] smp_apic_timer_interrupt+0xa9/0x250 [ 12.513876] apic_timer_interrupt+0xf/0x20 [ 12.514343] default_idle+0x1c/0x170 [ 12.514765] do_idle+0x199/0x240 [ 12.515159] cpu_startup_entry+0x19/0x20 [ 12.515614] start_kernel+0x422/0x42a [ 12.516045] secondary_startup_64+0xa4/0xb0 [ 12.516521] INITIAL USE at: [ 12.516774] _raw_spin_lock_irqsave+0x38/0x50 [ 12.517258] rq_attach_root+0x16/0xd0 [ 12.517685] sched_init+0x2f2/0x3eb [ 12.518096] start_kernel+0x1fb/0x42a [ 12.518525] secondary_startup_64+0xa4/0xb0 [ 12.518986] } [ 12.519132] ... key at: [<ffffffff82b7bc28>] __key.71384+0x0/0x8 [ 12.519649] ... acquired at: [ 12.519892] pcpu_freelist_pop+0x7b/0xd0 [ 12.520221] bpf_get_stackid+0x1d2/0x4d0 [ 12.520563] ___bpf_prog_run+0x8b4/0x11a0 [ 12.520887] [ 12.521008] -> (&head->lock){+...} { [ 12.521292] HARDIRQ-ON-W at: [ 12.521539] _raw_spin_lock+0x2f/0x40 [ 12.521950] pcpu_freelist_push+0x2a/0x40 [ 12.522396] bpf_get_stackid+0x494/0x4d0 [ 12.522828] ___bpf_prog_run+0x8b4/0x11a0 [ 12.523296] INITIAL USE at: [ 12.523537] _raw_spin_lock+0x2f/0x40 [ 12.523944] pcpu_freelist_populate+0xc0/0x120 [ 12.524417] htab_map_alloc+0x405/0x500 [ 12.524835] __do_sys_bpf+0x1a3/0x1a90 [ 12.525253] do_syscall_64+0x4a/0x180 [ 12.525659] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 12.526167] } [ 12.526311] ... key at: [<ffffffff838f7668>] __key.13130+0x0/0x8 [ 12.526812] ... acquired at: [ 12.527047] __lock_acquire+0x521/0x1350 [ 12.527371] lock_acquire+0x98/0x190 [ 12.527680] _raw_spin_lock+0x2f/0x40 [ 12.527994] pcpu_freelist_push+0x2a/0x40 [ 12.528325] bpf_get_stackid+0x494/0x4d0 [ 12.528645] ___bpf_prog_run+0x8b4/0x11a0 [ 12.528970] [ 12.529092] [ 12.529092] stack backtrace: [ 12.529444] CPU: 0 PID: 276 Comm: dd Not tainted 5.0.0-rc3-00018-g2fa53f892422 #475 [ 12.530043] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 [ 12.530750] Call Trace: [ 12.530948] dump_stack+0x5f/0x8b [ 12.531248] check_usage_backwards+0x10c/0x120 [ 12.531598] ? ___bpf_prog_run+0x8b4/0x11a0 [ 12.531935] ? mark_lock+0x382/0x560 [ 12.532229] mark_lock+0x382/0x560 [ 12.532496] ? print_shortest_lock_dependencies+0x180/0x180 [ 12.532928] __lock_acquire+0x521/0x1350 [ 12.533271] ? find_get_entry+0x17f/0x2e0 [ 12.533586] ? find_get_entry+0x19c/0x2e0 [ 12.533902] ? lock_acquire+0x98/0x190 [ 12.534196] lock_acquire+0x98/0x190 [ 12.534482] ? pcpu_freelist_push+0x2a/0x40 [ 12.534810] _raw_spin_lock+0x2f/0x40 [ 12.535099] ? pcpu_freelist_push+0x2a/0x40 [ 12.535432] pcpu_freelist_push+0x2a/0x40 [ 12.535750] bpf_get_stackid+0x494/0x4d0 [ 12.536062] ___bpf_prog_run+0x8b4/0x11a0 It has been explained that is a false positive here: https://lkml.org/lkml/2018/7/25/756 Recap: - stackmap uses pcpu_freelist - The lock in pcpu_freelist is a percpu lock - stackmap is only used by tracing bpf_prog - A tracing bpf_prog cannot be run if another bpf_prog has already been running (ensured by the percpu bpf_prog_active counter). Eric pointed out that this lockdep splats stops other legit lockdep splats in selftests/bpf/test_progs.c. Fix this by calling local_irq_save/restore for stackmap. Another false positive had also been worked around by calling local_irq_save in commit 89ad2fa3f043 ("bpf: fix lockdep splat"). That commit added unnecessary irq_save/restore to fast path of bpf hash map. irqs are already disabled at that point, since htab is holding per bucket spin_lock with irqsave. Let's reduce overhead for htab by introducing __pcpu_freelist_push/pop function w/o irqsave and convert pcpu_freelist_push/pop to irqsave to be used elsewhere (right now only in stackmap). It stops lockdep false positive in stackmap with a bit of acceptable overhead. Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation") Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Reported-by: Eric Dumazet <eric.dumazet@gmail.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
* bpf: Prevent memory disambiguation attackAlexei Starovoitov2018-12-051-4/+58
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit af86ca4e3088fe5eacf2f7e58c01fa68ca067672 upstream. Detect code patterns where malicious 'speculative store bypass' can be used and sanitize such patterns. 39: (bf) r3 = r10 40: (07) r3 += -216 41: (79) r8 = *(u64 *)(r7 +0) // slow read 42: (7a) *(u64 *)(r10 -72) = 0 // verifier inserts this instruction 43: (7b) *(u64 *)(r8 +0) = r3 // this store becomes slow due to r8 44: (79) r1 = *(u64 *)(r6 +0) // cpu speculatively executes this load 45: (71) r2 = *(u8 *)(r1 +0) // speculatively arbitrary 'load byte' // is now sanitized Above code after x86 JIT becomes: e5: mov %rbp,%rdx e8: add $0xffffffffffffff28,%rdx ef: mov 0x0(%r13),%r14 f3: movq $0x0,-0x48(%rbp) fb: mov %rdx,0x0(%r14) ff: mov 0x0(%rbx),%rdi 103: movzbq 0x0(%rdi),%rsi Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [bwh: Backported to 4.14: - Add bpf_verifier_env parameter to check_stack_write() - Look up stack slot_types with state->stack_slot_type[] rather than state->stack[].slot_type[] - Drop bpf_verifier_env argument to verbose() - Adjust context] Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: Sasha Levin <sashal@kernel.org>
* bpf: wait for running BPF programs when updating map-in-mapDaniel Colascione2018-11-131-0/+13
| | | | | | | | | | | | | | | | | | | | | | commit 1ae80cf31938c8f77c37a29bbe29e7f1cd492be8 upstream. The map-in-map frequently serves as a mechanism for atomic snapshotting of state that a BPF program might record. The current implementation is dangerous to use in this way, however, since userspace has no way of knowing when all programs that might have retrieved the "old" value of the map may have completed. This change ensures that map update operations on map-in-map map types always wait for all references to the old map to drop before returning to userspace. Signed-off-by: Daniel Colascione <dancol@google.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [fengc@google.com: 4.14 backport: adjust context] Signed-off-by: Chenbo Feng <fengc@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix partial copy of map_ptr when dst is scalarDaniel Borkmann2018-11-101-4/+6
| | | | | | | | | | | | | | | | | | | | commit 0962590e553331db2cc0aef2dc35c57f6300dbbe upstream. ALU operations on pointers such as scalar_reg += map_value_ptr are handled in adjust_ptr_min_max_vals(). Problem is however that map_ptr and range in the register state share a union, so transferring state through dst_reg->range = ptr_reg->range is just buggy as any new map_ptr in the dst_reg is then truncated (or null) for subsequent checks. Fix this by adding a raw member and use it for copying state over to dst_reg. Fixes: f1174f77b50c ("bpf/verifier: rework value tracking") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Edward Cree <ecree@solarflare.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* bpf: sockmap, map_release does not hold refcnt for pinned mapsJohn Fastabend2018-11-043-5/+6
| | | | | | | | | | | | | | | | | | [ Upstream commit ba6b8de423f8d0dee48d6030288ed81c03ddf9f0 ] Relying on map_release hook to decrement the reference counts when a map is removed only works if the map is not being pinned. In the pinned case the ref is decremented immediately and the BPF programs released. After this BPF programs may not be in-use which is not what the user would expect. This patch moves the release logic into bpf_map_put_uref() and brings sockmap in-line with how a similar case is handled in prog array maps. Fixes: 3d9e952697de ("bpf: sockmap, fix leaking maps with attached but not detached progs") Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
* bpf: 32-bit RSH verification must truncate input before the ALU opJann Horn2018-10-101-1/+9
| | | | | | | | | | | | | | | | | | | | | | | | | commit b799207e1e1816b09e7a5920fbb2d5fcf6edd681 upstream. When I wrote commit 468f6eafa6c4 ("bpf: fix 32-bit ALU op verification"), I assumed that, in order to emulate 64-bit arithmetic with 32-bit logic, it is sufficient to just truncate the output to 32 bits; and so I just moved the register size coercion that used to be at the start of the function to the end of the function. That assumption is true for almost every op, but not for 32-bit right shifts, because those can propagate information towards the least significant bit. Fix it by always truncating inputs for 32-bit ops to 32 bits. Also get rid of the coerce_reg_to_size() after the ALU op, since that has no effect. Fixes: 468f6eafa6c4 ("bpf: fix 32-bit ALU op verification") Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: sockmap: write_space events need to be passed to TCP handlerJohn Fastabend2018-10-031-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 9b2e0388bec8ec5427403e23faff3b58dd1c3200 ] When sockmap code is using the stream parser it also handles the write space events in order to handle the case where (a) verdict redirects skb to another socket and (b) the sockmap then sends the skb but due to memory constraints (or other EAGAIN errors) needs to do a retry. But the initial code missed a third case where the skb_send_sock_locked() triggers an sk_wait_event(). A typically case would be when sndbuf size is exceeded. If this happens because we do not pass the write_space event to the lower layers we never wake up the event and it will wait for sndtimeo. Which as noted in ktls fix may be rather large and look like a hang to the user. To reproduce the best test is to reduce the sndbuf size and send 1B data chunks to stress the memory handling. To fix this pass the event from the upper layer to the lower layer. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: hash map: decrement counter on errorMauricio Vasquez B2018-08-241-5/+11
| | | | | | | | | | | | | | [ Upstream commit ed2b82c03dc187018307c7c6bf9299705f3db383 ] Decrement the number of elements in the map in case the allocation of a new node fails. Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements") Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix references to free_bpf_prog_info() in commentsJakub Kicinski2018-08-031-2/+2
| | | | | | | | | | | | | | [ Upstream commit ab7f5bf0928be2f148d000a6eaa6c0a36e74750e ] Comments in the verifier refer to free_bpf_prog_info() which seems to have never existed in tree. Replace it with free_used_maps(). Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: sockmap, fix leaking maps with attached but not detached progsJohn Fastabend2018-04-261-5/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 3d9e952697de89b53227f06d4241f275eb99cfc4 ] When a program is attached to a map we increment the program refcnt to ensure that the program is not removed while it is potentially being referenced from sockmap side. However, if this same program also references the map (this is a reasonably common pattern in my programs) then the verifier will also increment the maps refcnt from the verifier. This is to ensure the map doesn't get garbage collected while the program has a reference to it. So we are left in a state where the map holds the refcnt on the program stopping it from being removed and releasing the map refcnt. And vice versa the program holds a refcnt on the map stopping it from releasing the refcnt on the prog. All this is fine as long as users detach the program while the map fd is still around. But, if the user omits this detach command we are left with a dangling map we can no longer release. To resolve this when the map fd is released decrement the program references and remove any reference from the map to the program. This fixes the issue with possibly dangling map and creates a user side API constraint. That is, the map fd must be held open for programs to be attached to a map. Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support") Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: skip unnecessary capability checkChenbo Feng2018-03-281-1/+1
| | | | | | | | | | | | | | | | | | commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream. The current check statement in BPF syscall will do a capability check for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This code path will trigger unnecessary security hooks on capability checking and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN access. This can be resolved by simply switch the order of the statement and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is allowed. Signed-off-by: Chenbo Feng <fengc@google.com> Acked-by: Lorenzo Colitti <lorenzo@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: allow xadd only on aligned memoryDaniel Borkmann2018-03-111-16/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ upstream commit ca36960211eb228bcbc7aaebfa0d027368a94c60 ] The requirements around atomic_add() / atomic64_add() resp. their JIT implementations differ across architectures. E.g. while x86_64 seems just fine with BPF's xadd on unaligned memory, on arm64 it triggers via interpreter but also JIT the following crash: [ 830.864985] Unable to handle kernel paging request at virtual address ffff8097d7ed6703 [...] [ 830.916161] Internal error: Oops: 96000021 [#1] SMP [ 830.984755] CPU: 37 PID: 2788 Comm: test_verifier Not tainted 4.16.0-rc2+ #8 [ 830.991790] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.29 07/17/2017 [ 830.998998] pstate: 80400005 (Nzcv daif +PAN -UAO) [ 831.003793] pc : __ll_sc_atomic_add+0x4/0x18 [ 831.008055] lr : ___bpf_prog_run+0x1198/0x1588 [ 831.012485] sp : ffff00001ccabc20 [ 831.015786] x29: ffff00001ccabc20 x28: ffff8017d56a0f00 [ 831.021087] x27: 0000000000000001 x26: 0000000000000000 [ 831.026387] x25: 000000c168d9db98 x24: 0000000000000000 [ 831.031686] x23: ffff000008203878 x22: ffff000009488000 [ 831.036986] x21: ffff000008b14e28 x20: ffff00001ccabcb0 [ 831.042286] x19: ffff0000097b5080 x18: 0000000000000a03 [ 831.047585] x17: 0000000000000000 x16: 0000000000000000 [ 831.052885] x15: 0000ffffaeca8000 x14: 0000000000000000 [ 831.058184] x13: 0000000000000000 x12: 0000000000000000 [ 831.063484] x11: 0000000000000001 x10: 0000000000000000 [ 831.068783] x9 : 0000000000000000 x8 : 0000000000000000 [ 831.074083] x7 : 0000000000000000 x6 : 000580d428000000 [ 831.079383] x5 : 0000000000000018 x4 : 0000000000000000 [ 831.084682] x3 : ffff00001ccabcb0 x2 : 0000000000000001 [ 831.089982] x1 : ffff8097d7ed6703 x0 : 0000000000000001 [ 831.095282] Process test_verifier (pid: 2788, stack limit = 0x0000000018370044) [ 831.102577] Call trace: [ 831.105012] __ll_sc_atomic_add+0x4/0x18 [ 831.108923] __bpf_prog_run32+0x4c/0x70 [ 831.112748] bpf_test_run+0x78/0xf8 [ 831.116224] bpf_prog_test_run_xdp+0xb4/0x120 [ 831.120567] SyS_bpf+0x77c/0x1110 [ 831.123873] el0_svc_naked+0x30/0x34 [ 831.127437] Code: 97fffe97 17ffffec 00000000 f9800031 (885f7c31) Reason for this is because memory is required to be aligned. In case of BPF, we always enforce alignment in terms of stack access, but not when accessing map values or packet data when the underlying arch (e.g. arm64) has CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS set. xadd on packet data that is local to us anyway is just wrong, so forbid this case entirely. The only place where xadd makes sense in fact are map values; xadd on stack is wrong as well, but it's been around for much longer. Specifically enforce strict alignment in case of xadd, so that we handle this case generically and avoid such crashes in the first place. Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: add schedule points in percpu arrays managementEric Dumazet2018-03-111-1/+4
| | | | | | | | | | | | | | | | | | | [ upstream commit 32fff239de37ef226d5b66329dd133f64d63b22d ] syszbot managed to trigger RCU detected stalls in bpf_array_free_percpu() It takes time to allocate a huge percpu map, but even more time to free it. Since we run in process context, use cond_resched() to yield cpu if needed. Fixes: a10423b87a7e ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix rcu lockdep warning for lpm_trie map_free callbackYonghong Song2018-03-111-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ upstream commit 6c5f61023c5b0edb0c8a64c902fe97c6453b1852 ] Commit 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function") fixed a memory leak and removed unnecessary locks in map_free callback function. Unfortrunately, it introduced a lockdep warning. When lockdep checking is turned on, running tools/testing/selftests/bpf/test_lpm_map will have: [ 98.294321] ============================= [ 98.294807] WARNING: suspicious RCU usage [ 98.295359] 4.16.0-rc2+ #193 Not tainted [ 98.295907] ----------------------------- [ 98.296486] /home/yhs/work/bpf/kernel/bpf/lpm_trie.c:572 suspicious rcu_dereference_check() usage! [ 98.297657] [ 98.297657] other info that might help us debug this: [ 98.297657] [ 98.298663] [ 98.298663] rcu_scheduler_active = 2, debug_locks = 1 [ 98.299536] 2 locks held by kworker/2:1/54: [ 98.300152] #0: ((wq_completion)"events"){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0 [ 98.301381] #1: ((work_completion)(&map->work)){+.+.}, at: [<00000000196bc1f0>] process_one_work+0x157/0x5c0 Since actual trie tree removal happens only after no other accesses to the tree are possible, replacing rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock)) with rcu_dereference_protected(*slot, 1) fixed the issue. Fixes: 9a3efb6b661f ("bpf: fix memory leak in lpm_trie map_free callback function") Reported-by: Eric Dumazet <edumazet@google.com> Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Yonghong Song <yhs@fb.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix memory leak in lpm_trie map_free callback functionYonghong Song2018-03-111-4/+7
| | | | | | | | | | | | | | | | | | | | | | [ upstream commit 9a3efb6b661f71d5675369ace9257833f0e78ef3 ] There is a memory leak happening in lpm_trie map_free callback function trie_free. The trie structure itself does not get freed. Also, trie_free function did not do synchronize_rcu before freeing various data structures. This is incorrect as some rcu_read_lock region(s) for lookup, update, delete or get_next_key may not complete yet. The fix is to add synchronize_rcu in the beginning of trie_free. The useless spin_lock is removed from this function as well. Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation") Reported-by: Mathieu Malaterre <malat@debian.org> Reported-by: Alexei Starovoitov <ast@kernel.org> Tested-by: Mathieu Malaterre <malat@debian.org> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix mlock precharge on arraymapsDaniel Borkmann2018-03-111-12/+16
| | | | | | | | | | | | | | | | | | | | | | | | [ upstream commit 9c2d63b843a5c8a8d0559cc067b5398aa5ec3ffc ] syzkaller recently triggered OOM during percpu map allocation; while there is work in progress by Dennis Zhou to add __GFP_NORETRY semantics for percpu allocator under pressure, there seems also a missing bpf_map_precharge_memlock() check in array map allocation. Given today the actual bpf_map_charge_memlock() happens after the find_and_alloc_map() in syscall path, the bpf_map_precharge_memlock() is there to bail out early before we go and do the map setup work when we find that we hit the limits anyway. Therefore add this for array map as well. Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements") Fixes: a10423b87a7e ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Reported-by: syzbot+adb03f3f0bb57ce3acda@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Dennis Zhou <dennisszhou@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: sockmap missing NULL psock checkJohn Fastabend2018-03-031-2/+9
| | | | | | | | | | | | | | | | | [ Upstream commit 5731a879d03bdaa00265f8ebc32dfd0e65d25276 ] Add psock NULL check to handle a racing sock event that can get the sk_callback_lock before this case but after xchg happens causing the refcnt to hit zero and sock user data (psock) to be null and queued for garbage collection. Also add a comment in the code because this is a bit subtle and not obvious in my opinion. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: mark dst unknown on inconsistent {s, u}bounds adjustmentsDaniel Borkmann2018-02-251-9/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 6f16101e6a8b4324c36e58a29d9e0dbb287cdedb upstream. syzkaller generated a BPF proglet and triggered a warning with the following: 0: (b7) r0 = 0 1: (d5) if r0 s<= 0x0 goto pc+0 R0=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0 2: (1f) r0 -= r1 R0=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0 verifier internal error: known but bad sbounds What happens is that in the first insn, r0's min/max value are both 0 due to the immediate assignment, later in the jsle test the bounds are updated for the min value in the false path, meaning, they yield smin_val = 1, smax_val = 0, and when ctx pointer is subtracted from r0, verifier bails out with the internal error and throwing a WARN since smin_val != smax_val for the known constant. For min_val > max_val scenario it means that reg_set_min_max() and reg_set_min_max_inv() (which both refine existing bounds) demonstrated that such branch cannot be taken at runtime. In above scenario for the case where it will be taken, the existing [0, 0] bounds are kept intact. Meaning, the rejection is not due to a verifier internal error, and therefore the WARN() is not necessary either. We could just reject such cases in adjust_{ptr,scalar}_min_max_vals() when either known scalars have smin_val != smax_val or umin_val != umax_val or any scalar reg with bounds smin_val > smax_val or umin_val > umax_val. However, there may be a small risk of breakage of buggy programs, so handle this more gracefully and in adjust_{ptr,scalar}_min_max_vals() just taint the dst reg as unknown scalar when we see ops with such kind of src reg. Reported-by: syzbot+6d362cadd45dc0a12ba4@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kmemcheck: remove annotationsLevin, Alexander (Sasha Levin)2018-02-221-6/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 4950276672fce5c241857540f8561c440663673d upstream. Patch series "kmemcheck: kill kmemcheck", v2. As discussed at LSF/MM, kill kmemcheck. KASan is a replacement that is able to work without the limitation of kmemcheck (single CPU, slow). KASan is already upstream. We are also not aware of any users of kmemcheck (or users who don't consider KASan as a suitable replacement). The only objection was that since KASAN wasn't supported by all GCC versions provided by distros at that time we should hold off for 2 years, and try again. Now that 2 years have passed, and all distros provide gcc that supports KASAN, kill kmemcheck again for the very same reasons. This patch (of 4): Remove kmemcheck annotations, and calls to kmemcheck from the kernel. [alexander.levin@verizon.com: correctly remove kmemcheck call from dma_map_sg_attrs] Link: http://lkml.kernel.org/r/20171012192151.26531-1-alexander.levin@verizon.com Link: http://lkml.kernel.org/r/20171007030159.22241-2-alexander.levin@verizon.com Signed-off-by: Sasha Levin <alexander.levin@verizon.com> Cc: Alexander Potapenko <glider@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tim Hansen <devtimhansen@gmail.com> Cc: Vegard Nossum <vegardno@ifi.uio.no> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: reject stores into ctx via st and xaddDaniel Borkmann2018-01-311-0/+19
| | | | | | | | | | | | | | | | | | | [ upstream commit f37a8cb84cce18762e8f86a70bd6a49a66ab964c ] Alexei found that verifier does not reject stores into context via BPF_ST instead of BPF_STX. And while looking at it, we also should not allow XADD variant of BPF_STX. The context rewriter is only assuming either BPF_LDX_MEM- or BPF_STX_MEM-type operations, thus reject anything other than that so that assumptions in the rewriter properly hold. Add test cases as well for BPF selftests. Fixes: d691f9e8d440 ("bpf: allow programs to write to certain skb fields") Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix 32-bit divide by zeroAlexei Starovoitov2018-01-311-0/+18
| | | | | | | | | | | | | | | [ upstream commit 68fda450a7df51cff9e5a4d4a4d9d0d5f2589153 ] due to some JITs doing if (src_reg == 0) check in 64-bit mode for div/mod operations mask upper 32-bits of src register before doing the check Fixes: 622582786c9e ("net: filter: x86: internal BPF JIT") Fixes: 7a12b5031c6b ("sparc64: Add eBPF JIT.") Reported-by: syzbot+48340bb518e88849e2e3@syzkaller.appspotmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix divides by zeroEric Dumazet2018-01-311-2/+2
| | | | | | | | | | | | | | | [ upstream commit c366287ebd698ef5e3de300d90cd62ee9ee7373e ] Divides by zero are not nice, lets avoid them if possible. Also do_div() seems not needed when dealing with 32bit operands, but this seems a minor detail. Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: introduce BPF_JIT_ALWAYS_ON configAlexei Starovoitov2018-01-311-0/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ upstream commit 290af86629b25ffd1ed6232c4e9107da031705cb ] The BPF interpreter has been used as part of the spectre 2 attack CVE-2017-5715. A quote from goolge project zero blog: "At this point, it would normally be necessary to locate gadgets in the host kernel code that can be used to actually leak data by reading from an attacker-controlled location, shifting and masking the result appropriately and then using the result of that as offset to an attacker-controlled address for a load. But piecing gadgets together and figuring out which ones work in a speculation context seems annoying. So instead, we decided to use the eBPF interpreter, which is built into the host kernel - while there is no legitimate way to invoke it from inside a VM, the presence of the code in the host kernel's text section is sufficient to make it usable for the attack, just like with ordinary ROP gadgets." To make attacker job harder introduce BPF_JIT_ALWAYS_ON config option that removes interpreter from the kernel in favor of JIT-only mode. So far eBPF JIT is supported by: x64, arm64, arm32, sparc64, s390, powerpc64, mips64 The start of JITed program is randomized and code page is marked as read-only. In addition "constant blinding" can be turned on with net.core.bpf_jit_harden v2->v3: - move __bpf_prog_ret0 under ifdef (Daniel) v1->v2: - fix init order, test_bpf and cBPF (Daniel's feedback) - fix offloaded bpf (Jakub's feedback) - add 'return 0' dummy in case something can invoke prog->bpf_func - retarget bpf tree. For bpf-next the patch would need one extra hunk. It will be sent when the trees are merged back to net-next Considered doing: int bpf_jit_enable __read_mostly = BPF_EBPF_JIT_DEFAULT; but it seems better to land the patch as-is and in bpf-next remove bpf_jit_enable global variable from all JITs, consolidate in one place and remove this jit_init() function. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: arsh is not supported in 32 bit alu thus reject itDaniel Borkmann2018-01-171-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | commit 7891a87efc7116590eaba57acc3c422487802c6f upstream. The following snippet was throwing an 'unknown opcode cc' warning in BPF interpreter: 0: (18) r0 = 0x0 2: (7b) *(u64 *)(r10 -16) = r0 3: (cc) (u32) r0 s>>= (u32) r0 4: (95) exit Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X} generation, not all of them do and interpreter does neither. We can leave existing ones and implement it later in bpf-next for the remaining ones, but reject this properly in verifier for the time being. Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)") Reported-by: syzbot+93c4904c5c70348a6890@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf, array: fix overflow in max_entries and undefined behavior in index_maskDaniel Borkmann2018-01-171-3/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit bbeb6e4323dad9b5e0ee9f60c223dd532e2403b1 upstream. syzkaller tried to alloc a map with 0xfffffffd entries out of a userns, and thus unprivileged. With the recently added logic in b2157399cc98 ("bpf: prevent out-of-bounds speculation") we round this up to the next power of two value for max_entries for unprivileged such that we can apply proper masking into potentially zeroed out map slots. However, this will generate an index_mask of 0xffffffff, and therefore a + 1 will let this overflow into new max_entries of 0. This will pass allocation, etc, and later on map access we still enforce on the original attr->max_entries value which was 0xfffffffd, therefore triggering GPF all over the place. Thus bail out on overflow in such case. Moreover, on 32 bit archs roundup_pow_of_two() can also not be used, since fls_long(max_entries - 1) can result in 32 and 1UL << 32 in 32 bit space is undefined. Therefore, do this by hand in a 64 bit variable. This fixes all the issues triggered by syzkaller's reproducers. Fixes: b2157399cc98 ("bpf: prevent out-of-bounds speculation") Reported-by: syzbot+b0efb8e572d01bce1ae0@syzkaller.appspotmail.com Reported-by: syzbot+6c15e9744f75f2364773@syzkaller.appspotmail.com Reported-by: syzbot+d2f5524fb46fd3b312ee@syzkaller.appspotmail.com Reported-by: syzbot+61d23c95395cc90dbc2b@syzkaller.appspotmail.com Reported-by: syzbot+0d363c942452cca68c01@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: prevent out-of-bounds speculationAlexei Starovoitov2018-01-172-11/+72
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit b2157399cc9898260d6031c5bfe45fe137c1fbe7 upstream. Under speculation, CPUs may mis-predict branches in bounds checks. Thus, memory accesses under a bounds check may be speculated even if the bounds check fails, providing a primitive for building a side channel. To avoid leaking kernel data round up array-based maps and mask the index after bounds check, so speculated load with out of bounds index will load either valid value from the array or zero from the padded area. Unconditionally mask index for all array types even when max_entries are not rounded to power of 2 for root user. When map is created by unpriv user generate a sequence of bpf insns that includes AND operation to make sure that JITed code includes the same 'index & index_mask' operation. If prog_array map is created by unpriv user replace bpf_tail_call(ctx, map, index); with if (index >= max_entries) { index &= map->index_mask; bpf_tail_call(ctx, map, index); } (along with roundup to power 2) to prevent out-of-bounds speculation. There is secondary redundant 'if (index >= max_entries)' in the interpreter and in all JITs, but they can be optimized later if necessary. Other array-like maps (cpumap, devmap, sockmap, perf_event_array, cgroup_array) cannot be used by unpriv, so no changes there. That fixes bpf side of "Variant 1: bounds check bypass (CVE-2017-5753)" on all architectures with and without JIT. v2->v3: Daniel noticed that attack potentially can be crafted via syscall commands without loading the program, so add masking to those paths as well. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* bpf: fix integer overflowsDaniel Borkmann2017-12-251-0/+48
| | | | | | | | | | | | | | | | | | | | | | | | | From: Alexei Starovoitov <ast@kernel.org> [ Upstream commit bb7f0f989ca7de1153bd128a40a71709e339fa03 ] There were various issues related to the limited size of integers used in the verifier: - `off + size` overflow in __check_map_access() - `off + reg->off` overflow in check_mem_access() - `off + reg->var_off.value` overflow or 32-bit truncation of `reg->var_off.value` in check_mem_access() - 32-bit truncation in check_stack_boundary() Make sure that any integer math cannot overflow by not allowing pointer math with large values. Also reduce the scope of "scalar op scalar" tracking. Fixes: f1174f77b50c ("bpf/verifier: rework value tracking") Reported-by: Jann Horn <jannh@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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