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* bpf: add initial bpf tracepointsDaniel Borkmann2017-01-253-3/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This work adds a number of tracepoints to paths that are either considered slow-path or exception-like states, where monitoring or inspecting them would be desirable. For bpf(2) syscall, tracepoints have been placed for main commands when they succeed. In XDP case, tracepoint is for exceptions, that is, f.e. on abnormal BPF program exit such as unknown or XDP_ABORTED return code, or when error occurs during XDP_TX action and the packet could not be forwarded. Both have been split into separate event headers, and can be further extended. Worst case, if they unexpectedly should get into our way in future, they can also removed [1]. Of course, these tracepoints (like any other) can be analyzed by eBPF itself, etc. Example output: # ./perf record -a -e bpf:* sleep 10 # ./perf script sock_example 6197 [005] 283.980322: bpf:bpf_map_create: map type=ARRAY ufd=4 key=4 val=8 max=256 flags=0 sock_example 6197 [005] 283.980721: bpf:bpf_prog_load: prog=a5ea8fa30ea6849c type=SOCKET_FILTER ufd=5 sock_example 6197 [005] 283.988423: bpf:bpf_prog_get_type: prog=a5ea8fa30ea6849c type=SOCKET_FILTER sock_example 6197 [005] 283.988443: bpf:bpf_map_lookup_elem: map type=ARRAY ufd=4 key=[06 00 00 00] val=[00 00 00 00 00 00 00 00] [...] sock_example 6197 [005] 288.990868: bpf:bpf_map_lookup_elem: map type=ARRAY ufd=4 key=[01 00 00 00] val=[14 00 00 00 00 00 00 00] swapper 0 [005] 289.338243: bpf:bpf_prog_put_rcu: prog=a5ea8fa30ea6849c type=SOCKET_FILTER [1] https://lwn.net/Articles/705270/ Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* trace: add variant without spacing in trace_print_hex_seqDaniel Borkmann2017-01-251-3/+4
| | | | | | | | | | | | For upcoming tracepoint support for BPF, we want to dump the program's tag. Format should be similar to __print_hex(), but without spacing. Add a __print_hex_str() variant for exactly that purpose that reuses trace_print_hex_seq(). Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* bpf: enable verifier to better track const alu opsDaniel Borkmann2017-01-241-19/+45
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | William reported couple of issues in relation to direct packet access. Typical scheme is to check for data + [off] <= data_end, where [off] can be either immediate or coming from a tracked register that contains an immediate, depending on the branch, we can then access the data. However, in case of calculating [off] for either the mentioned test itself or for access after the test in a more "complex" way, then the verifier will stop tracking the CONST_IMM marked register and will mark it as UNKNOWN_VALUE one. Adding that UNKNOWN_VALUE typed register to a pkt() marked register, the verifier then bails out in check_packet_ptr_add() as it finds the registers imm value below 48. In the first below example, that is due to evaluate_reg_imm_alu() not handling right shifts and thus marking the register as UNKNOWN_VALUE via helper __mark_reg_unknown_value() that resets imm to 0. In the second case the same happens at the time when r4 is set to r4 &= r5, where it transitions to UNKNOWN_VALUE from evaluate_reg_imm_alu(). Later on r4 we shift right by 3 inside evaluate_reg_alu(), where the register's imm turns into 3. That is, for registers with type UNKNOWN_VALUE, imm of 0 means that we don't know what value the register has, and for imm > 0 it means that the value has [imm] upper zero bits. F.e. when shifting an UNKNOWN_VALUE register by 3 to the right, no matter what value it had, we know that the 3 upper most bits must be zero now. This is to make sure that ALU operations with unknown registers don't overflow. Meaning, once we know that we have more than 48 upper zero bits, or, in other words cannot go beyond 0xffff offset with ALU ops, such an addition will track the target register as a new pkt() register with a new id, but 0 offset and 0 range, so for that a new data/data_end test will be required. Is the source register a CONST_IMM one that is to be added to the pkt() register, or the source instruction is an add instruction with immediate value, then it will get added if it stays within max 0xffff bounds. >From there, pkt() type, can be accessed should reg->off + imm be within the access range of pkt(). [...] from 28 to 30: R0=imm1,min_value=1,max_value=1 R1=pkt(id=0,off=0,r=22) R2=pkt_end R3=imm144,min_value=144,max_value=144 R4=imm0,min_value=0,max_value=0 R5=inv48,min_value=2054,max_value=2054 R10=fp 30: (bf) r5 = r3 31: (07) r5 += 23 32: (77) r5 >>= 3 33: (bf) r6 = r1 34: (0f) r6 += r5 cannot add integer value with 0 upper zero bits to ptr_to_packet [...] from 52 to 80: R0=imm1,min_value=1,max_value=1 R1=pkt(id=0,off=0,r=34) R2=pkt_end R3=inv R4=imm272 R5=inv56,min_value=17,max_value=17 R6=pkt(id=0,off=26,r=34) R10=fp 80: (07) r4 += 71 81: (18) r5 = 0xfffffff8 83: (5f) r4 &= r5 84: (77) r4 >>= 3 85: (0f) r1 += r4 cannot add integer value with 3 upper zero bits to ptr_to_packet Thus to get above use-cases working, evaluate_reg_imm_alu() has been extended for further ALU ops. This is fine, because we only operate strictly within realm of CONST_IMM types, so here we don't care about overflows as they will happen in the simulated but also real execution and interaction with pkt() in check_packet_ptr_add() will check actual imm value once added to pkt(), but it's irrelevant before. With regards to 06c1c049721a ("bpf: allow helpers access to variable memory") that works on UNKNOWN_VALUE registers, the verifier becomes now a bit smarter as it can better resolve ALU ops, so we need to adapt two test cases there, as min/max bound tracking only becomes necessary when registers were spilled to stack. So while mask was set before to track upper bound for UNKNOWN_VALUE case, it's now resolved directly as CONST_IMM, and such contructs are only necessary when f.e. registers are spilled. For commit 6b17387307ba ("bpf: recognize 64bit immediate loads as consts") that initially enabled dw load tracking only for nfp jit/ analyzer, I did couple of tests on large, complex programs and we don't increase complexity badly (my tests were in ~3% range on avg). I've added a couple of tests similar to affected code above, and it works fine with verifier now. Reported-by: William Tu <u9012063@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Gianluca Borello <g.borello@gmail.com> Cc: William Tu <u9012063@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* bpf, lpm: fix kfree of im_node in trie_update_elemDaniel Borkmann2017-01-231-1/+1
| | | | | | | | | | We need to initialize im_node to NULL, otherwise in case of error path it gets passed to kfree() as uninitialized pointer. Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* bpf: add a longest prefix match trie map implementationDaniel Mack2017-01-232-1/+504
| | | | | | | | | | | | | | | | | | | | This trie implements a longest prefix match algorithm that can be used to match IP addresses to a stored set of ranges. Internally, data is stored in an unbalanced trie of nodes that has a maximum height of n, where n is the prefixlen the trie was created with. Tries may be created with prefix lengths that are multiples of 8, in the range from 8 to 2048. The key used for lookup and update operations is a struct bpf_lpm_trie_key, and the value is a uint64_t. The code carries more information about the internal implementation. Signed-off-by: Daniel Mack <daniel@zonque.org> Reviewed-by: David Herrmann <dh.herrmann@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* bpf: add bpf_probe_read_str helperGianluca Borello2017-01-201-0/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Provide a simple helper with the same semantics of strncpy_from_unsafe(): int bpf_probe_read_str(void *dst, int size, const void *unsafe_addr) This gives more flexibility to a bpf program. A typical use case is intercepting a file name during sys_open(). The current approach is: SEC("kprobe/sys_open") void bpf_sys_open(struct pt_regs *ctx) { char buf[PATHLEN]; // PATHLEN is defined to 256 bpf_probe_read(buf, sizeof(buf), ctx->di); /* consume buf */ } This is suboptimal because the size of the string needs to be estimated at compile time, causing more memory to be copied than often necessary, and can become more problematic if further processing on buf is done, for example by pushing it to userspace via bpf_perf_event_output(), since the real length of the string is unknown and the entire buffer must be copied (and defining an unrolled strnlen() inside the bpf program is a very inefficient and unfeasible approach). With the new helper, the code can easily operate on the actual string length rather than the buffer size: SEC("kprobe/sys_open") void bpf_sys_open(struct pt_regs *ctx) { char buf[PATHLEN]; // PATHLEN is defined to 256 int res = bpf_probe_read_str(buf, sizeof(buf), ctx->di); /* consume buf, for example push it to userspace via * bpf_perf_event_output(), but this time we can use * res (the string length) as event size, after checking * its boundaries. */ } Another useful use case is when parsing individual process arguments or individual environment variables navigating current->mm->arg_start and current->mm->env_start: using this helper and the return value, one can quickly iterate at the right offset of the memory area. The code changes simply leverage the already existent strncpy_from_unsafe() kernel function, which is safe to be called from a bpf program as it is used in bpf_trace_printk(). Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
* Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netDavid S. Miller2017-01-179-59/+169
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| * Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netLinus Torvalds2017-01-173-11/+13
| |\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull networking fixes from David Miller: 1) Handle multicast packets properly in fast-RX path of mac80211, from Johannes Berg. 2) Because of a logic bug, the user can't actually force SW checksumming on r8152 devices. This makes diagnosis of hw checksumming bugs really annoying. Fix from Hayes Wang. 3) VXLAN route lookup does not take the source and destination ports into account, which means IPSEC policies cannot be matched properly. Fix from Martynas Pumputis. 4) Do proper RCU locking in netvsc callbacks, from Stephen Hemminger. 5) Fix SKB leaks in mlxsw driver, from Arkadi Sharshevsky. 6) If lwtunnel_fill_encap() fails, we do not abort the netlink message construction properly in fib_dump_info(), from David Ahern. 7) Do not use kernel stack for DMA buffers in atusb driver, from Stefan Schmidt. 8) Openvswitch conntack actions need to maintain a correct checksum, fix from Lance Richardson. 9) ax25_disconnect() is missing a check for ax25->sk being NULL, in fact it already checks this, but not in all of the necessary spots. Fix from Basil Gunn. 10) Action GET operations in the packet scheduler can erroneously bump the reference count of the entry, making it unreleasable. Fix from Jamal Hadi Salim. Jamal gives a great set of example command lines that trigger this in the commit message. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (46 commits) net sched actions: fix refcnt when GETing of action after bind net/mlx4_core: Eliminate warning messages for SRQ_LIMIT under SRIOV net/mlx4_core: Fix when to save some qp context flags for dynamic VST to VGT transitions net/mlx4_core: Fix racy CQ (Completion Queue) free net: stmmac: don't use netdev_[dbg, info, ..] before net_device is registered net/mlx5e: Fix a -Wmaybe-uninitialized warning ax25: Fix segfault after sock connection timeout bpf: rework prog_digest into prog_tag tipc: allocate user memory with GFP_KERNEL flag net: phy: dp83867: allow RGMII_TXID/RGMII_RXID interface types ip6_tunnel: Account for tunnel header in tunnel MTU mld: do not remove mld souce list info when set link down be2net: fix MAC addr setting on privileged BE3 VFs be2net: don't delete MAC on close on unprivileged BE3 VFs be2net: fix status check in be_cmd_pmac_add() cpmac: remove hopeless #warning ravb: do not use zero-length alignment DMA descriptor mlx4: do not call napi_schedule() without care openvswitch: maintain correct checksum state in conntrack actions tcp: fix tcp_fastopen unaligned access complaints on sparc ...
| | * bpf: rework prog_digest into prog_tagDaniel Borkmann2017-01-163-11/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 7bd509e311f4 ("bpf: add prog_digest and expose it via fdinfo/netlink") was recently discussed, partially due to admittedly suboptimal name of "prog_digest" in combination with sha1 hash usage, thus inevitably and rightfully concerns about its security in terms of collision resistance were raised with regards to use-cases. The intended use cases are for debugging resp. introspection only for providing a stable "tag" over the instruction sequence that both kernel and user space can calculate independently. It's not usable at all for making a security relevant decision. So collisions where two different instruction sequences generate the same tag can happen, but ideally at a rather low rate. The "tag" will be dumped in hex and is short enough to introspect in tracepoints or kallsyms output along with other data such as stack trace, etc. Thus, this patch performs a rename into prog_tag and truncates the tag to a short output (64 bits) to make it obvious it's not collision-free. Should in future a hash or facility be needed with a security relevant focus, then we can think about requirements, constraints, etc that would fit to that situation. For now, rework the exposed parts for the current use cases as long as nothing has been released yet. Tested on x86_64 and s390x. Fixes: 7bd509e311f4 ("bpf: add prog_digest and expose it via fdinfo/netlink") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
| * | Merge branch 'for-linus' of ↵Linus Torvalds2017-01-151-4/+6
| |\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull namespace fixes from Eric Biederman: "This tree contains 4 fixes. The first is a fix for a race that can causes oopses under the right circumstances, and that someone just recently encountered. Past that are several small trivial correct fixes. A real issue that was blocking development of an out of tree driver, but does not appear to have caused any actual problems for in-tree code. A potential deadlock that was reported by lockdep. And a deadlock people have experienced and took the time to track down caused by a cleanup that removed the code to drop a reference count" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sysctl: Drop reference added by grab_header in proc_sys_readdir pid: fix lockdep deadlock warning due to ucount_lock libfs: Modify mount_pseudo_xattr to be clear it is not a userspace mount mnt: Protect the mountpoint hashtable with mount_lock
| | * | pid: fix lockdep deadlock warning due to ucount_lockAndrei Vagin2017-01-101-4/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ========================================================= [ INFO: possible irq lock inversion dependency detected ] 4.10.0-rc2-00024-g4aecec9-dirty #118 Tainted: G W --------------------------------------------------------- swapper/1/0 just changed the state of lock: (&(&sighand->siglock)->rlock){-.....}, at: [<ffffffffbd0a1bc6>] __lock_task_sighand+0xb6/0x2c0 but this lock took another, HARDIRQ-unsafe lock in the past: (ucounts_lock){+.+...} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Chain exists of: &(&sighand->siglock)->rlock --> &(&tty->ctrl_lock)->rlock --> ucounts_lock Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(ucounts_lock); local_irq_disable(); lock(&(&sighand->siglock)->rlock); lock(&(&tty->ctrl_lock)->rlock); <Interrupt> lock(&(&sighand->siglock)->rlock); *** DEADLOCK *** This patch removes a dependency between rlock and ucount_lock. Fixes: f333c700c610 ("pidns: Add a limit on the number of pid namespaces") Cc: stable@vger.kernel.org Signed-off-by: Andrei Vagin <avagin@openvz.org> Acked-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
| * | | Merge branch 'timers-urgent-for-linus' of ↵Linus Torvalds2017-01-152-2/+9
| |\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull NOHZ fix from Ingo Molnar: "This fixes an old NOHZ race where we incorrectly calculate the next timer interrupt in certain circumstances where hrtimers are pending, that can cause hard to reproduce stalled-values artifacts in /proc/stat" * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: nohz: Fix collision between tick and other hrtimers
| | * | | nohz: Fix collision between tick and other hrtimersFrederic Weisbecker2017-01-112-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the tick is stopped and an interrupt occurs afterward, we check on that interrupt exit if the next tick needs to be rescheduled. If it doesn't need any update, we don't want to do anything. In order to check if the tick needs an update, we compare it against the clockevent device deadline. Now that's a problem because the clockevent device is at a lower level than the tick itself if it is implemented on top of hrtimer. Every hrtimer share this clockevent device. So comparing the next tick deadline against the clockevent device deadline is wrong because the device may be programmed for another hrtimer whose deadline collides with the tick. As a result we may end up not reprogramming the tick accidentally. In a worst case scenario under full dynticks mode, the tick stops firing as it is supposed to every 1hz, leaving /proc/stat stalled: Task in a full dynticks CPU ---------------------------- * hrtimer A is queued 2 seconds ahead * the tick is stopped, scheduled 1 second ahead * tick fires 1 second later * on tick exit, nohz schedules the tick 1 second ahead but sees the clockevent device is already programmed to that deadline, fooled by hrtimer A, the tick isn't rescheduled. * hrtimer A is cancelled before its deadline * tick never fires again until an interrupt happens... In order to fix this, store the next tick deadline to the tick_sched local structure and reuse that value later to check whether we need to reprogram the clock after an interrupt. On the other hand, ts->sleep_length still wants to know about the next clock event and not just the tick, so we want to improve the related comment to avoid confusion. Reported-by: James Hartsock <hartsjc@redhat.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Wanpeng Li <wanpeng.li@hotmail.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Rik van Riel <riel@redhat.com> Link: http://lkml.kernel.org/r/1483539124-5693-1-git-send-email-fweisbec@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | | | Merge branch 'perf-urgent-for-linus' of ↵Linus Torvalds2017-01-151-42/+133
| |\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull perf fixes from Ingo Molnar: "Misc race fixes uncovered by fuzzing efforts, a Sparse fix, two PMU driver fixes, plus miscellanous tooling fixes" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf/x86: Reject non sampling events with precise_ip perf/x86/intel: Account interrupts for PEBS errors perf/core: Fix concurrent sys_perf_event_open() vs. 'move_group' race perf/core: Fix sys_perf_event_open() vs. hotplug perf/x86/intel: Use ULL constant to prevent undefined shift behaviour perf/x86/intel/uncore: Fix hardcoded socket 0 assumption in the Haswell init code perf/x86: Set pmu->module in Intel PMU modules perf probe: Fix to probe on gcc generated symbols for offline kernel perf probe: Fix --funcs to show correct symbols for offline module perf symbols: Robustify reading of build-id from sysfs perf tools: Install tools/lib/traceevent plugins with install-bin tools lib traceevent: Fix prev/next_prio for deadline tasks perf record: Fix --switch-output documentation and comment perf record: Make __record_options static tools lib subcmd: Add OPT_STRING_OPTARG_SET option perf probe: Fix to get correct modname from elf header samples/bpf trace_output_user: Remove duplicate sys/ioctl.h include samples/bpf sock_example: Avoid getting ethhdr from two includes perf sched timehist: Show total scheduling time
| | * | | | perf/x86/intel: Account interrupts for PEBS errorsJiri Olsa2017-01-141-16/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It's possible to set up PEBS events to get only errors and not any data, like on SNB-X (model 45) and IVB-EP (model 62) via 2 perf commands running simultaneously: taskset -c 1 ./perf record -c 4 -e branches:pp -j any -C 10 This leads to a soft lock up, because the error path of the intel_pmu_drain_pebs_nhm() does not account event->hw.interrupt for error PEBS interrupts, so in case you're getting ONLY errors you don't have a way to stop the event when it's over the max_samples_per_tick limit: NMI watchdog: BUG: soft lockup - CPU#22 stuck for 22s! [perf_fuzzer:5816] ... RIP: 0010:[<ffffffff81159232>] [<ffffffff81159232>] smp_call_function_single+0xe2/0x140 ... Call Trace: ? trace_hardirqs_on_caller+0xf5/0x1b0 ? perf_cgroup_attach+0x70/0x70 perf_install_in_context+0x199/0x1b0 ? ctx_resched+0x90/0x90 SYSC_perf_event_open+0x641/0xf90 SyS_perf_event_open+0x9/0x10 do_syscall_64+0x6c/0x1f0 entry_SYSCALL64_slow_path+0x25/0x25 Add perf_event_account_interrupt() which does the interrupt and frequency checks and call it from intel_pmu_drain_pebs_nhm()'s error path. We keep the pending_kill and pending_wakeup logic only in the __perf_event_overflow() path, because they make sense only if there's any data to deliver. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vince@deater.net> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/1482931866-6018-2-git-send-email-jolsa@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| | * | | | perf/core: Fix concurrent sys_perf_event_open() vs. 'move_group' racePeter Zijlstra2017-01-141-4/+54
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Di Shen reported a race between two concurrent sys_perf_event_open() calls where both try and move the same pre-existing software group into a hardware context. The problem is exactly that described in commit: f63a8daa5812 ("perf: Fix event->ctx locking") ... where, while we wait for a ctx->mutex acquisition, the event->ctx relation can have changed under us. That very same commit failed to recognise sys_perf_event_context() as an external access vector to the events and thereby didn't apply the established locking rules correctly. So while one sys_perf_event_open() call is stuck waiting on mutex_lock_double(), the other (which owns said locks) moves the group about. So by the time the former sys_perf_event_open() acquires the locks, the context we've acquired is stale (and possibly dead). Apply the established locking rules as per perf_event_ctx_lock_nested() to the mutex_lock_double() for the 'move_group' case. This obviously means we need to validate state after we acquire the locks. Reported-by: Di Shen (Keen Lab) Tested-by: John Dias <joaodias@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Min Chong <mchong@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Fixes: f63a8daa5812 ("perf: Fix event->ctx locking") Link: http://lkml.kernel.org/r/20170106131444.GZ3174@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| | * | | | perf/core: Fix sys_perf_event_open() vs. hotplugPeter Zijlstra2017-01-141-22/+48
| | | |/ / | | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There is problem with installing an event in a task that is 'stuck' on an offline CPU. Blocked tasks are not dis-assosciated from offlined CPUs, after all, a blocked task doesn't run and doesn't require a CPU etc.. Only on wakeup do we ammend the situation and place the task on a available CPU. If we hit such a task with perf_install_in_context() we'll loop until either that task wakes up or the CPU comes back online, if the task waking depends on the event being installed, we're stuck. While looking into this issue, I also spotted another problem, if we hit a task with perf_install_in_context() that is in the middle of being migrated, that is we observe the old CPU before sending the IPI, but run the IPI (on the old CPU) while the task is already running on the new CPU, things also go sideways. Rework things to rely on task_curr() -- outside of rq->lock -- which is rather tricky. Imagine the following scenario where we're trying to install the first event into our task 't': CPU0 CPU1 CPU2 (current == t) t->perf_event_ctxp[] = ctx; smp_mb(); cpu = task_cpu(t); switch(t, n); migrate(t, 2); switch(p, t); ctx = t->perf_event_ctxp[]; // must not be NULL smp_function_call(cpu, ..); generic_exec_single() func(); spin_lock(ctx->lock); if (task_curr(t)) // false add_event_to_ctx(); spin_unlock(ctx->lock); perf_event_context_sched_in(); spin_lock(ctx->lock); // sees event So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'. Because if CPU2's load of that variable were to observe NULL, it would not try to schedule the ctx and we'd have a task running without its counter, which would be 'bad'. As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it first and not see the event yet, then CPU0 must observe task_curr() and retry. If the install happens first, then we must see the event on sched-in and all is well. I think we can translate the first part (until the 'must not be NULL') of the scenario to a litmus test like: C C-peterz { } P0(int *x, int *y) { int r1; WRITE_ONCE(*x, 1); smp_mb(); r1 = READ_ONCE(*y); } P1(int *y, int *z) { WRITE_ONCE(*y, 1); smp_store_release(z, 1); } P2(int *x, int *z) { int r1; int r2; r1 = smp_load_acquire(z); smp_mb(); r2 = READ_ONCE(*x); } exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0) Where: x is perf_event_ctxp[], y is our tasks's CPU, and z is our task being placed on the rq of CPU2. The P0 smp_mb() is the one added by this patch, ordering the store to perf_event_ctxp[] from find_get_context() and the load of task_cpu() in task_function_call(). The smp_store_release/smp_load_acquire model the RCpc locking of the rq->lock and the smp_mb() of P2 is the context switch switching from whatever CPU2 was running to our task 't'. This litmus test evaluates into: Test C-peterz Allowed States 7 0:r1=0; 2:r1=0; 2:r2=0; 0:r1=0; 2:r1=0; 2:r2=1; 0:r1=0; 2:r1=1; 2:r2=1; 0:r1=1; 2:r1=0; 2:r2=0; 0:r1=1; 2:r1=0; 2:r2=1; 0:r1=1; 2:r1=1; 2:r2=0; 0:r1=1; 2:r1=1; 2:r2=1; No Witnesses Positive: 0 Negative: 7 Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0) Observation C-peterz Never 0 7 Hash=e427f41d9146b2a5445101d3e2fcaa34 And the strong and weak model agree. Reported-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: Will Deacon <will.deacon@arm.com> Cc: jeremy.linton@arm.com Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | | Merge tag 'vfio-v4.10-rc4' of git://github.com/awilliam/linux-vfioLinus Torvalds2017-01-131-0/+1
| |\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull VFIO fixes from Alex Williamson: - Cleanups and bug fixes for the mtty sample driver (Dan Carpenter) - Export and make use of has_capability() to fix incorrect use of ns_capable() for testing task capabilities (Jike Song) * tag 'vfio-v4.10-rc4' of git://github.com/awilliam/linux-vfio: vfio/type1: Remove pid_namespace.h include vfio iommu type1: fix the testing of capability for remote task capability: export has_capability vfio-mdev: remove some dead code vfio-mdev: buffer overflow in ioctl() vfio-mdev: return -EFAULT if copy_to_user() fails
| | * | | | capability: export has_capabilityJike Song2017-01-121-0/+1
| | | |/ / | | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | has_capability() is sometimes needed by modules to test capability for specified task other than current, so export it. Cc: Kirti Wankhede <kwankhede@nvidia.com> Signed-off-by: Jike Song <jike.song@intel.com> Acked-by: Serge Hallyn <serge@hallyn.com> Acked-by: James Morris <james.l.morris@oracle.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
| * | | | Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvmLinus Torvalds2017-01-131-0/+7
| |\ \ \ \ | | |_|_|/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull KVM fixes from Paolo Bonzini: - fix for module unload vs deferred jump labels (note: there might be other buggy modules!) - two NULL pointer dereferences from syzkaller - also syzkaller: fix emulation of fxsave/fxrstor/sgdt/sidt, problem made worse during this merge window, "just" kernel memory leak on releases - fix emulation of "mov ss" - somewhat serious on AMD, less so on Intel * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: KVM: x86: fix emulation of "MOV SS, null selector" KVM: x86: fix NULL deref in vcpu_scan_ioapic KVM: eventfd: fix NULL deref irqbypass consumer KVM: x86: Introduce segmented_write_std KVM: x86: flush pending lapic jump label updates on module unload jump_labels: API for flushing deferred jump label updates
| | * | | jump_labels: API for flushing deferred jump label updatesDavid Matlack2017-01-121-0/+7
| | |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Modules that use static_key_deferred need a way to synchronize with any delayed work that is still pending when the module is unloaded. Introduce static_key_deferred_flush() which flushes any pending jump label updates. Signed-off-by: David Matlack <dmatlack@google.com> Cc: stable@vger.kernel.org Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
* | | | bpf, trace: make ctx access checks more robustDaniel Borkmann2017-01-161-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make sure that ctx cannot potentially be accessed oob by asserting explicitly that ctx access size into pt_regs for BPF_PROG_TYPE_KPROBE programs must be within limits. In case some 32bit archs have pt_regs not being a multiple of 8, then BPF_DW access could cause such access. BPF_PROG_TYPE_KPROBE progs don't have a ctx conversion function since there's no extra mapping needed. kprobe_prog_is_valid_access() didn't enforce sizeof(long) as the only allowed access size, since LLVM can generate non BPF_W/BPF_DW access to regs from time to time. For BPF_PROG_TYPE_TRACEPOINT we don't have a ctx conversion either, so add a BUILD_BUG_ON() check to make sure that BPF_DW access will not be a similar issue in future (ctx works on event buffer as opposed to pt_regs there). Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | | bpf: allow b/h/w/dw access for bpf's cb in ctxDaniel Borkmann2017-01-121-2/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When structs are used to store temporary state in cb[] buffer that is used with programs and among tail calls, then the generated code will not always access the buffer in bpf_w chunks. We can ease programming of it and let this act more natural by allowing for aligned b/h/w/dw sized access for cb[] ctx member. Various test cases are attached as well for the selftest suite. Potentially, this can also be reused for other program types to pass data around. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | | bpf: pass original insn directly to convert_ctx_accessDaniel Borkmann2017-01-122-9/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, when calling convert_ctx_access() callback for the various program types, we pass in insn->dst_reg, insn->src_reg, insn->off from the original instruction. This information is needed to rewrite the instruction that is based on the user ctx structure into a kernel representation for the ctx. As we'd like to allow access size beyond just BPF_W, we'd need also insn->code for that in order to decode the original access size. Given that, lets just pass insn directly to the convert_ctx_access() callback and work on that to not clutter the callback with even more arguments we need to pass when everything is already contained in insn. So lets go through that once, no functional change. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | | Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/netDavid S. Miller2017-01-114-4/+8
|\| | | | | | | | | | | | | | | | | | | | | | | | | | | Two AF_* families adding entries to the lockdep tables at the same time. Signed-off-by: David S. Miller <davem@davemloft.net>
| * | | signal: protect SIGNAL_UNKILLABLE from unintentional clearing.Jamie Iles2017-01-101-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since commit 00cd5c37afd5 ("ptrace: permit ptracing of /sbin/init") we can now trace init processes. init is initially protected with SIGNAL_UNKILLABLE which will prevent fatal signals such as SIGSTOP, but there are a number of paths during tracing where SIGNAL_UNKILLABLE can be implicitly cleared. This can result in init becoming stoppable/killable after tracing. For example, running: while true; do kill -STOP 1; done & strace -p 1 and then stopping strace and the kill loop will result in init being left in state TASK_STOPPED. Sending SIGCONT to init will resume it, but init will now respond to future SIGSTOP signals rather than ignoring them. Make sure that when setting SIGNAL_STOP_CONTINUED/SIGNAL_STOP_STOPPED that we don't clear SIGNAL_UNKILLABLE. Link: http://lkml.kernel.org/r/20170104122017.25047-1-jamie.iles@oracle.com Signed-off-by: Jamie Iles <jamie.iles@oracle.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | mm: fix devm_memremap_pages crash, use mem_hotplug_{begin, done}Dan Williams2017-01-101-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Both arch_add_memory() and arch_remove_memory() expect a single threaded context. For example, arch/x86/mm/init_64.c::kernel_physical_mapping_init() does not hold any locks over this check and branch: if (pgd_val(*pgd)) { pud = (pud_t *)pgd_page_vaddr(*pgd); paddr_last = phys_pud_init(pud, __pa(vaddr), __pa(vaddr_end), page_size_mask); continue; } pud = alloc_low_page(); paddr_last = phys_pud_init(pud, __pa(vaddr), __pa(vaddr_end), page_size_mask); The result is that two threads calling devm_memremap_pages() simultaneously can end up colliding on pgd initialization. This leads to crash signatures like the following where the loser of the race initializes the wrong pgd entry: BUG: unable to handle kernel paging request at ffff888ebfff0000 IP: memcpy_erms+0x6/0x10 PGD 2f8e8fc067 PUD 0 /* <---- Invalid PUD */ Oops: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 54 PID: 3818 Comm: systemd-udevd Not tainted 4.6.7+ #13 task: ffff882fac290040 ti: ffff882f887a4000 task.ti: ffff882f887a4000 RIP: memcpy_erms+0x6/0x10 [..] Call Trace: ? pmem_do_bvec+0x205/0x370 [nd_pmem] ? blk_queue_enter+0x3a/0x280 pmem_rw_page+0x38/0x80 [nd_pmem] bdev_read_page+0x84/0xb0 Hold the standard memory hotplug mutex over calls to arch_{add,remove}_memory(). Fixes: 41e94a851304 ("add devm_memremap_pages") Link: http://lkml.kernel.org/r/148357647831.9498.12606007370121652979.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Christoph Hellwig <hch@lst.de> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| * | | bpf: do not use KMALLOC_SHIFT_MAXMichal Hocko2017-01-102-2/+2
| |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 01b3f52157ff ("bpf: fix allocation warnings in bpf maps and integer overflow") has added checks for the maximum allocateable size. It (ab)used KMALLOC_SHIFT_MAX for that purpose. While this is not incorrect it is not very clean because we already have KMALLOC_MAX_SIZE for this very reason so let's change both checks to use KMALLOC_MAX_SIZE instead. The original motivation for using KMALLOC_SHIFT_MAX was to work around an incorrect KMALLOC_MAX_SIZE which could lead to allocation warnings but it is no longer needed since "slab: make sure that KMALLOC_MAX_SIZE will fit into MAX_ORDER". Link: http://lkml.kernel.org/r/20161220130659.16461-3-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | bpf: Make unnecessarily global functions staticTobias Klauser2017-01-101-7/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the functions __local_list_pop_free(), __local_list_pop_pending(), bpf_common_lru_populate() and bpf_percpu_lru_populate() static as they are not used outide of bpf_lru_list.c This fixes the following GCC warnings when building with 'W=1': kernel/bpf/bpf_lru_list.c:363:22: warning: no previous prototype for ‘__local_list_pop_free’ [-Wmissing-prototypes] kernel/bpf/bpf_lru_list.c:376:22: warning: no previous prototype for ‘__local_list_pop_pending’ [-Wmissing-prototypes] kernel/bpf/bpf_lru_list.c:560:6: warning: no previous prototype for ‘bpf_common_lru_populate’ [-Wmissing-prototypes] kernel/bpf/bpf_lru_list.c:577:6: warning: no previous prototype for ‘bpf_percpu_lru_populate’ [-Wmissing-prototypes] Cc: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Tobias Klauser <tklauser@distanz.ch> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()Tobias Klauser2017-01-101-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Remove the unused but set variable 'first_node' in __bpf_lru_list_shrink_inactive() to fix the following GCC warning when building with 'W=1': kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable] Cc: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Tobias Klauser <tklauser@distanz.ch> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: rename ARG_PTR_TO_STACKAlexei Starovoitov2017-01-093-26/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | since ARG_PTR_TO_STACK is no longer just pointer to stack rename it to ARG_PTR_TO_MEM and adjust comment. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: allow helpers access to variable memoryGianluca Borello2017-01-091-10/+64
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, helpers that read and write from/to the stack can do so using a pair of arguments of type ARG_PTR_TO_STACK and ARG_CONST_STACK_SIZE. ARG_CONST_STACK_SIZE accepts a constant register of type CONST_IMM, so that the verifier can safely check the memory access. However, requiring the argument to be a constant can be limiting in some circumstances. Since the current logic keeps track of the minimum and maximum value of a register throughout the simulated execution, ARG_CONST_STACK_SIZE can be changed to also accept an UNKNOWN_VALUE register in case its boundaries have been set and the range doesn't cause invalid memory accesses. One common situation when this is useful: int len; char buf[BUFSIZE]; /* BUFSIZE is 128 */ if (some_condition) len = 42; else len = 84; some_helper(..., buf, len & (BUFSIZE - 1)); The compiler can often decide to assign the constant values 42 or 48 into a variable on the stack, instead of keeping it in a register. When the variable is then read back from stack into the register in order to be passed to the helper, the verifier will not be able to recognize the register as constant (the verifier is not currently tracking all constant writes into memory), and the program won't be valid. However, by allowing the helper to accept an UNKNOWN_VALUE register, this program will work because the bitwise AND operation will set the range of possible values for the UNKNOWN_VALUE register to [0, BUFSIZE), so the verifier can guarantee the helper call will be safe (assuming the argument is of type ARG_CONST_STACK_SIZE_OR_ZERO, otherwise one more check against 0 would be needed). Custom ranges can be set not only with ALU operations, but also by explicitly comparing the UNKNOWN_VALUE register with constants. Another very common example happens when intercepting system call arguments and accessing user-provided data of variable size using bpf_probe_read(). One can load at runtime the user-provided length in an UNKNOWN_VALUE register, and then read that exact amount of data up to a compile-time determined limit in order to fit into the proper local storage allocated on the stack, without having to guess a suboptimal access size at compile time. Also, in case the helpers accepting the UNKNOWN_VALUE register operate in raw mode, disable the raw mode so that the program is required to initialize all memory, since there is no guarantee the helper will fill it completely, leaving possibilities for data leak (just relevant when the memory used by the helper is the stack, not when using a pointer to map element value or packet). In other words, ARG_PTR_TO_RAW_STACK will be treated as ARG_PTR_TO_STACK. Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: allow adjusted map element values to spillGianluca Borello2017-01-091-5/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | commit 484611357c19 ("bpf: allow access into map value arrays") introduces the ability to do pointer math inside a map element value via the PTR_TO_MAP_VALUE_ADJ register type. The current support doesn't handle the case where a PTR_TO_MAP_VALUE_ADJ is spilled into the stack, limiting several use cases, especially when generating bpf code from a compiler. Handle this case by explicitly enabling the register type PTR_TO_MAP_VALUE_ADJ to be spilled. Also, make sure that min_value and max_value are reset just for BPF_LDX operations that don't result in a restore of a spilled register from stack. Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: allow helpers access to map element valuesGianluca Borello2017-01-091-2/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Enable helpers to directly access a map element value by passing a register type PTR_TO_MAP_VALUE (or PTR_TO_MAP_VALUE_ADJ) to helper arguments ARG_PTR_TO_STACK or ARG_PTR_TO_RAW_STACK. This enables several use cases. For example, a typical tracing program might want to capture pathnames passed to sys_open() with: struct trace_data { char pathname[PATHLEN]; }; SEC("kprobe/sys_open") void bpf_sys_open(struct pt_regs *ctx) { struct trace_data data; bpf_probe_read(data.pathname, sizeof(data.pathname), ctx->di); /* consume data.pathname, for example via * bpf_trace_printk() or bpf_perf_event_output() */ } Such a program could easily hit the stack limit in case PATHLEN needs to be large or more local variables need to exist, both of which are quite common scenarios. Allowing direct helper access to map element values, one could do: struct bpf_map_def SEC("maps") scratch_map = { .type = BPF_MAP_TYPE_PERCPU_ARRAY, .key_size = sizeof(u32), .value_size = sizeof(struct trace_data), .max_entries = 1, }; SEC("kprobe/sys_open") int bpf_sys_open(struct pt_regs *ctx) { int id = 0; struct trace_data *p = bpf_map_lookup_elem(&scratch_map, &id); if (!p) return; bpf_probe_read(p->pathname, sizeof(p->pathname), ctx->di); /* consume p->pathname, for example via * bpf_trace_printk() or bpf_perf_event_output() */ } And wouldn't risk exhausting the stack. Code changes are loosely modeled after commit 6841de8b0d03 ("bpf: allow helpers access the packet directly"). Unlike with PTR_TO_PACKET, these changes just work with ARG_PTR_TO_STACK and ARG_PTR_TO_RAW_STACK (not ARG_PTR_TO_MAP_KEY, ARG_PTR_TO_MAP_VALUE, ...): adding those would be trivial, but since there is not currently a use case for that, it's reasonable to limit the set of changes. Also, add new tests to make sure accesses to map element values from helpers never go out of boundary, even when adjusted. Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | | bpf: split check_mem_access logic for map valuesGianluca Borello2017-01-091-39/+49
|/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Move the logic to check memory accesses to a PTR_TO_MAP_VALUE_ADJ from check_mem_access() to a separate helper check_map_access_adj(). This enables to use those checks in other parts of the verifier as well, where boundaries on PTR_TO_MAP_VALUE_ADJ might need to be checked, for example when checking helper function arguments. The same thing is already happening for other types such as PTR_TO_PACKET and its check_packet_access() helper. The code has been copied verbatim, with the only difference of removing the "off += reg->max_value" statement and moving the sum into the call statement to check_map_access(), as that was only needed due to the earlier common check_map_access() call. Signed-off-by: Gianluca Borello <g.borello@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* | Merge branch 'stable-4.10' of git://git.infradead.org/users/pcmoore/auditLinus Torvalds2017-01-051-4/+14
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | Pull audit fixes from Paul Moore: "Two small fixes relating to audit's use of fsnotify. The first patch plugs a leak and the second fixes some lock shenanigans. The patches are small and I banged on this for an afternoon with our testsuite and didn't see anything odd" * 'stable-4.10' of git://git.infradead.org/users/pcmoore/audit: audit: Fix sleep in atomic fsnotify: Remove fsnotify_duplicate_mark()
| * audit: Fix sleep in atomicJan Kara2017-01-031-4/+14
| | | | | | | | | | | | | | | | | | | | | | | | Audit tree code was happily adding new notification marks while holding spinlocks. Since fsnotify_add_mark() acquires group->mark_mutex this can lead to sleeping while holding a spinlock, deadlocks due to lock inversion, and probably other fun. Fix the problem by acquiring group->mark_mutex earlier. CC: Paul Moore <paul@paul-moore.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Paul Moore <paul@paul-moore.com>
| * fsnotify: Remove fsnotify_duplicate_mark()Jan Kara2016-12-231-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are only two calls sites of fsnotify_duplicate_mark(). Those are in kernel/audit_tree.c and both are bogus. Vfsmount pointer is unused for audit tree, inode pointer and group gets set in fsnotify_add_mark_locked() later anyway, mask and free_mark are already set in alloc_chunk(). In fact, calling fsnotify_duplicate_mark() is actively harmful because following fsnotify_add_mark_locked() will leak group reference by overwriting the group pointer. So just remove the two calls to fsnotify_duplicate_mark() and the function. Signed-off-by: Jan Kara <jack@suse.cz> [PM: line wrapping to fit in 80 chars] Signed-off-by: Paul Moore <paul@paul-moore.com>
* | smp/hotplug: Undo tglxs brainfartThomas Gleixner2016-12-261-1/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | The attempt to prevent overwriting an active state resulted in a disaster which effectively disables all dynamically allocated hotplug states. Cleanup the mess. Fixes: dc280d936239 ("cpu/hotplug: Prevent overwriting of callbacks") Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge branch 'timers-urgent-for-linus' of ↵Linus Torvalds2016-12-2524-147/+144
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer type cleanups from Thomas Gleixner: "This series does a tree wide cleanup of types related to timers/timekeeping. - Get rid of cycles_t and use a plain u64. The type is not really helpful and caused more confusion than clarity - Get rid of the ktime union. The union has become useless as we use the scalar nanoseconds storage unconditionally now. The 32bit timespec alike storage got removed due to the Y2038 limitations some time ago. That leaves the odd union access around for no reason. Clean it up. Both changes have been done with coccinelle and a small amount of manual mopping up" * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: ktime: Get rid of ktime_equal() ktime: Cleanup ktime_set() usage ktime: Get rid of the union clocksource: Use a plain u64 instead of cycle_t
| * | ktime: Cleanup ktime_set() usageThomas Gleixner2016-12-255-7/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ktime_set(S,N) was required for the timespec storage type and is still useful for situations where a Seconds and Nanoseconds part of a time value needs to be converted. For anything where the Seconds argument is 0, this is pointless and can be replaced with a simple assignment. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org>
| * | ktime: Get rid of the unionThomas Gleixner2016-12-2513-88/+88
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ktime is a union because the initial implementation stored the time in scalar nanoseconds on 64 bit machine and in a endianess optimized timespec variant for 32bit machines. The Y2038 cleanup removed the timespec variant and switched everything to scalar nanoseconds. The union remained, but become completely pointless. Get rid of the union and just keep ktime_t as simple typedef of type s64. The conversion was done with coccinelle and some manual mopping up. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org>
| * | clocksource: Use a plain u64 instead of cycle_tThomas Gleixner2016-12-2510-52/+49
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There is no point in having an extra type for extra confusion. u64 is unambiguous. Conversion was done with the following coccinelle script: @rem@ @@ -typedef u64 cycle_t; @fix@ typedef cycle_t; @@ -cycle_t +u64 Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: John Stultz <john.stultz@linaro.org>
* | | Merge branch 'smp-urgent-for-linus' of ↵Linus Torvalds2016-12-251-184/+51
|\ \ \ | |/ / |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull SMP hotplug notifier removal from Thomas Gleixner: "This is the final cleanup of the hotplug notifier infrastructure. The series has been reintgrated in the last two days because there came a new driver using the old infrastructure via the SCSI tree. Summary: - convert the last leftover drivers utilizing notifiers - fixup for a completely broken hotplug user - prevent setup of already used states - removal of the notifiers - treewide cleanup of hotplug state names - consolidation of state space There is a sphinx based documentation pending, but that needs review from the documentation folks" * 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: irqchip/armada-xp: Consolidate hotplug state space irqchip/gic: Consolidate hotplug state space coresight/etm3/4x: Consolidate hotplug state space cpu/hotplug: Cleanup state names cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions staging/lustre/libcfs: Convert to hotplug state machine scsi/bnx2i: Convert to hotplug state machine scsi/bnx2fc: Convert to hotplug state machine cpu/hotplug: Prevent overwriting of callbacks x86/msr: Remove bogus cleanup from the error path bus: arm-ccn: Prevent hotplug callback leak perf/x86/intel/cstate: Prevent hotplug callback leak ARM/imx/mmcd: Fix broken cpu hotplug handling scsi: qedi: Convert to hotplug state machine
| * | cpu/hotplug: Remove obsolete cpu hotplug register/unregister functionsThomas Gleixner2016-12-251-138/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | hotcpu_notifier(), cpu_notifier(), __hotcpu_notifier(), __cpu_notifier(), register_hotcpu_notifier(), register_cpu_notifier(), __register_hotcpu_notifier(), __register_cpu_notifier(), unregister_hotcpu_notifier(), unregister_cpu_notifier(), __unregister_hotcpu_notifier(), __unregister_cpu_notifier() are unused now. Remove them and all related code. Remove also the now pointless cpu notifier error injection mechanism. The states can be executed step by step and error rollback is the same as cpu down, so any state transition can be tested w/o requiring the notifier error injection. Some CPU hotplug states are kept as they are (ab)used for hotplug state tracking. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20161221192112.005642358@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | cpu/hotplug: Prevent overwriting of callbacksThomas Gleixner2016-12-251-46/+50
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Developers manage to overwrite states blindly without thought. That's fatal and hard to debug. Add sanity checks to make it fail. This requries to restructure the code so that the dynamic state allocation happens in the same lock protected section as the actual store. Otherwise the previous assignment of 'Reserved' to the name field would trigger the overwrite check. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Link: http://lkml.kernel.org/r/20161221192111.675234535@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | | Replace <asm/uaccess.h> with <linux/uaccess.h> globallyLinus Torvalds2016-12-2429-29/+29
|/ / | | | | | | | | | | | | | | | | | | | | | | | | This was entirely automated, using the script by Al: PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>' sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \ $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h) to do the replacement at the end of the merge window. Requested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge branch 'perf-urgent-for-linus' of ↵Linus Torvalds2016-12-231-1/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull perf fixes from Ingo Molnar: "On the kernel side there's two x86 PMU driver fixes and a uprobes fix, plus on the tooling side there's a number of fixes and some late updates" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits) perf sched timehist: Fix invalid period calculation perf sched timehist: Remove hardcoded 'comm_width' check at print_summary perf sched timehist: Enlarge default 'comm_width' perf sched timehist: Honour 'comm_width' when aligning the headers perf/x86: Fix overlap counter scheduling bug perf/x86/pebs: Fix handling of PEBS buffer overflows samples/bpf: Move open_raw_sock to separate header samples/bpf: Remove perf_event_open() declaration samples/bpf: Be consistent with bpf_load_program bpf_insn parameter tools lib bpf: Add bpf_prog_{attach,detach} samples/bpf: Switch over to libbpf perf diff: Do not overwrite valid build id perf annotate: Don't throw error for zero length symbols perf bench futex: Fix lock-pi help string perf trace: Check if MAP_32BIT is defined (again) samples/bpf: Make perf_event_read() static uprobes: Fix uprobes on MIPS, allow for a cache flush after ixol breakpoint creation samples/bpf: Make samples more libbpf-centric tools lib bpf: Add flags to bpf_create_map() tools lib bpf: use __u32 from linux/types.h ...
| * | uprobes: Fix uprobes on MIPS, allow for a cache flush after ixol breakpoint ↵Marcin Nowakowski2016-12-181-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | creation Commit: 72e6ae285a1d ('ARM: 8043/1: uprobes need icache flush after xol write' ... has introduced an arch-specific method to ensure all caches are flushed appropriately after an instruction is written to an XOL page. However, when the XOL area is created and the out-of-line breakpoint instruction is copied, caches are not flushed at all and stale data may be found in icache. Replace a simple copy_to_page() with arch_uprobe_copy_ixol() to allow the arch to ensure all caches are updated accordingly. This change fixes uprobes on MIPS InterAptiv (tested on Creator Ci40). Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Victor Kamensky <victor.kamensky@linaro.org> Cc: linux-mips@linux-mips.org Link: http://lkml.kernel.org/r/1481625657-22850-1-git-send-email-marcin.nowakowski@imgtec.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | | Merge branch 'for-linus' of ↵Linus Torvalds2016-12-231-0/+3
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull final vfs updates from Al Viro: "Assorted cleanups and fixes all over the place" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: sg_write()/bsg_write() is not fit to be called under KERNEL_DS ufs: fix function declaration for ufs_truncate_blocks fs: exec: apply CLOEXEC before changing dumpable task flags seq_file: reset iterator to first record for zero offset vfs: fix isize/pos/len checks for reflink & dedupe [iov_iter] fix iterate_all_kinds() on empty iterators move aio compat to fs/aio.c reorganize do_make_slave() clone_private_mount() doesn't need to touch namespace_sem remove a bogus claim about namespace_sem being held by callers of mnt_alloc_id()
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