From 7d1982b4e335c1b184406b7566f6041bfe313c35 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 15 Jun 2018 02:30:47 +0200 Subject: bpf: fix panic in prog load calls cleanup While testing I found that when hitting error path in bpf_prog_load() where we jump to free_used_maps and prog contained BPF to BPF calls that were JITed earlier, then we never clean up the bpf_prog_kallsyms_add() done under jit_subprogs(). Add proper API to make BPF kallsyms deletion more clear and fix that. Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs") Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov --- kernel/bpf/core.c | 14 ++++++++++++++ kernel/bpf/syscall.c | 8 ++------ 2 files changed, 16 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 9f1493705f40..1061968adcc1 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -350,6 +350,20 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, return prog_adj; } +void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp) +{ + int i; + + for (i = 0; i < fp->aux->func_cnt; i++) + bpf_prog_kallsyms_del(fp->aux->func[i]); +} + +void bpf_prog_kallsyms_del_all(struct bpf_prog *fp) +{ + bpf_prog_kallsyms_del_subprogs(fp); + bpf_prog_kallsyms_del(fp); +} + #ifdef CONFIG_BPF_JIT /* All BPF JIT sysctl knobs here. */ int bpf_jit_enable __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_ALWAYS_ON); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0fa20624707f..0f62692fe635 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1034,14 +1034,9 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu) static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock) { if (atomic_dec_and_test(&prog->aux->refcnt)) { - int i; - /* bpf_prog_free_id() must be called first */ bpf_prog_free_id(prog, do_idr_lock); - - for (i = 0; i < prog->aux->func_cnt; i++) - bpf_prog_kallsyms_del(prog->aux->func[i]); - bpf_prog_kallsyms_del(prog); + bpf_prog_kallsyms_del_all(prog); call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu); } @@ -1384,6 +1379,7 @@ static int bpf_prog_load(union bpf_attr *attr) return err; free_used_maps: + bpf_prog_kallsyms_del_subprogs(prog); free_used_maps(prog->aux); free_prog: bpf_prog_uncharge_memlock(prog); -- cgit v1.2.3 From 9facc336876f7ecf9edba4c67b90426fde4ec898 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 15 Jun 2018 02:30:48 +0200 Subject: bpf: reject any prog that failed read-only lock We currently lock any JITed image as read-only via bpf_jit_binary_lock_ro() as well as the BPF image as read-only through bpf_prog_lock_ro(). In the case any of these would fail we throw a WARN_ON_ONCE() in order to yell loudly to the log. Perhaps, to some extend, this may be comparable to an allocation where __GFP_NOWARN is explicitly not set. Added via 65869a47f348 ("bpf: improve read-only handling"), this behavior is slightly different compared to any of the other in-kernel set_memory_ro() users who do not check the return code of set_memory_ro() and friends /at all/ (e.g. in the case of module_enable_ro() / module_disable_ro()). Given in BPF this is mandatory hardening step, we want to know whether there are any issues that would leave both BPF data writable. So it happens that syzkaller enabled fault injection and it triggered memory allocation failure deep inside x86's change_page_attr_set_clr() which was triggered from set_memory_ro(). Now, there are two options: i) leaving everything as is, and ii) reworking the image locking code in order to have a final checkpoint out of the central bpf_prog_select_runtime() which probes whether any of the calls during prog setup weren't successful, and then bailing out with an error. Option ii) is a better approach since this additional paranoia avoids altogether leaving any potential W+X pages from BPF side in the system. Therefore, lets be strict about it, and reject programs in such unlikely occasion. While testing I noticed also that one bpf_prog_lock_ro() call was missing on the outer dummy prog in case of calls, e.g. in the destructor we call bpf_prog_free_deferred() on the main prog where we try to bpf_prog_unlock_free() the program, and since we go via bpf_prog_select_runtime() do that as well. Reported-by: syzbot+3b889862e65a98317058@syzkaller.appspotmail.com Reported-by: syzbot+9e762b52dd17e616a7a5@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov --- kernel/bpf/core.c | 55 +++++++++++++++++++++++++++++++++++++++++++++------- kernel/bpf/syscall.c | 4 +--- 2 files changed, 49 insertions(+), 10 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 1061968adcc1..a9e6c04d0f4a 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -598,6 +598,8 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, bpf_fill_ill_insns(hdr, size); hdr->pages = size / PAGE_SIZE; + hdr->locked = 0; + hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)), PAGE_SIZE - sizeof(*hdr)); start = (get_random_int() % hole) & ~(alignment - 1); @@ -1448,6 +1450,33 @@ static int bpf_check_tail_call(const struct bpf_prog *fp) return 0; } +static int bpf_prog_check_pages_ro_locked(const struct bpf_prog *fp) +{ +#ifdef CONFIG_ARCH_HAS_SET_MEMORY + int i, err; + + for (i = 0; i < fp->aux->func_cnt; i++) { + err = bpf_prog_check_pages_ro_single(fp->aux->func[i]); + if (err) + return err; + } + + return bpf_prog_check_pages_ro_single(fp); +#endif + return 0; +} + +static void bpf_prog_select_func(struct bpf_prog *fp) +{ +#ifndef CONFIG_BPF_JIT_ALWAYS_ON + u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1); + + fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1]; +#else + fp->bpf_func = __bpf_prog_ret0_warn; +#endif +} + /** * bpf_prog_select_runtime - select exec runtime for BPF program * @fp: bpf_prog populated with internal BPF program @@ -1458,13 +1487,13 @@ static int bpf_check_tail_call(const struct bpf_prog *fp) */ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) { -#ifndef CONFIG_BPF_JIT_ALWAYS_ON - u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1); + /* In case of BPF to BPF calls, verifier did all the prep + * work with regards to JITing, etc. + */ + if (fp->bpf_func) + goto finalize; - fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1]; -#else - fp->bpf_func = __bpf_prog_ret0_warn; -#endif + bpf_prog_select_func(fp); /* eBPF JITs can rewrite the program in case constant * blinding is active. However, in case of error during @@ -1485,6 +1514,8 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) if (*err) return fp; } + +finalize: bpf_prog_lock_ro(fp); /* The tail call compatibility check can only be done at @@ -1493,7 +1524,17 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) * all eBPF JITs might immediately support all features. */ *err = bpf_check_tail_call(fp); - + if (*err) + return fp; + + /* Checkpoint: at this point onwards any cBPF -> eBPF or + * native eBPF program is read-only. If we failed to change + * the page attributes (e.g. allocation failure from + * splitting large pages), then reject the whole program + * in order to guarantee not ending up with any W+X pages + * from BPF side in kernel. + */ + *err = bpf_prog_check_pages_ro_locked(fp); return fp; } EXPORT_SYMBOL_GPL(bpf_prog_select_runtime); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0f62692fe635..35dc466641f2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1353,9 +1353,7 @@ static int bpf_prog_load(union bpf_attr *attr) if (err < 0) goto free_used_maps; - /* eBPF program is ready to be JITed */ - if (!prog->bpf_func) - prog = bpf_prog_select_runtime(prog, &err); + prog = bpf_prog_select_runtime(prog, &err); if (err < 0) goto free_used_maps; -- cgit v1.2.3 From 6d5fc1957989266006db6ef3dfb9159b42cf0189 Mon Sep 17 00:00:00 2001 From: Toshiaki Makita Date: Thu, 14 Jun 2018 11:07:42 +0900 Subject: xdp: Fix handling of devmap in generic XDP Commit 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") changed the return value type of __devmap_lookup_elem() from struct net_device * to struct bpf_dtab_netdev * but forgot to modify generic XDP code accordingly. Thus generic XDP incorrectly used struct bpf_dtab_netdev where struct net_device is expected, then skb->dev was set to invalid value. v2: - Fix compiler warning without CONFIG_BPF_SYSCALL. Fixes: 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") Signed-off-by: Toshiaki Makita Acked-by: Yonghong Song Acked-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann --- kernel/bpf/devmap.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index a7cc7b3494a9..642c97f6d1b8 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -345,6 +345,20 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp, return bq_enqueue(dst, xdpf, dev_rx); } +int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb, + struct bpf_prog *xdp_prog) +{ + int err; + + err = __xdp_generic_ok_fwd_dev(skb, dst->dev); + if (unlikely(err)) + return err; + skb->dev = dst->dev; + generic_xdp_tx(skb, xdp_prog); + + return 0; +} + static void *dev_map_lookup_elem(struct bpf_map *map, void *key) { struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key); -- cgit v1.2.3