- Dec 10, 2021
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SeongJae Park authored
Patch series "mm/damon: Fix fake /proc/loadavg reports", v3. This patchset fixes DAMON's fake load report issue. The first patch makes yet another variant of usleep_range() for this fix, and the second patch fixes the issue of DAMON by making it using the newly introduced function. This patch (of 2): Some kernel threads such as DAMON could need to repeatedly sleep in micro seconds level. Because usleep_range() sleeps in uninterruptible state, however, such threads would make /proc/loadavg reports fake load. To help such cases, this commit implements a variant of usleep_range() called usleep_idle_range(). It is same to usleep_range() but sets the state of the current task as TASK_IDLE while sleeping. Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org Signed-off-by:
SeongJae Park <sj@kernel.org> Suggested-by:
Andrew Morton <akpm@linux-foundation.org> Reviewed-by:
Thomas Gleixner <tglx@linutronix.de> Tested-by:
Oleksandr Natalenko <oleksandr@natalenko.name> Cc: John Stultz <john.stultz@linaro.org> Cc: <stable@vger.kernel.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- Dec 09, 2021
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Eric Biggers authored
Several ->poll() implementations are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'. However, that has a bug: wake_up_poll() calls __wake_up() with nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters, and the wakeup function for the first one returns a positive value, only that one will be called. That's *not* what's needed for POLLFREE; POLLFREE is special in that it really needs to wake up everyone. Considering the three non-blocking poll systems: - io_uring poll doesn't handle POLLFREE at all, so it is broken anyway. - aio poll is unaffected, since it doesn't support exclusive waits. However, that's fragile, as someone could add this feature later. - epoll doesn't appear to be broken by this, since its wakeup function returns 0 when it sees POLLFREE. But this is fragile. Although there is a workaround (see epoll), it's better to define a function which always sends POLLFREE to all waiters. Add such a function. Also make it verify that the queue really becomes empty after all waiters have been woken up. Reported-by:
Eric Biggers <ebiggers@google.com>
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Miaoqian Lin authored
There's error paths in __create_synth_event() after the argv is allocated that fail to free it. Add a jump to free it when necessary. Link: https://lkml.kernel.org/r/20211209024317.11783-1-linmq006@gmail.com Suggested-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by:
Miaoqian Lin <linmq006@gmail.com> [ Fixed up the patch and change log ] Signed-off-by:
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- Dec 08, 2021
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Jiri Olsa authored
Adding ops cleanup to unregister_ftrace_direct_multi, so it can be reused in another register call. Link: https://lkml.kernel.org/r/20211206182032.87248-3-jolsa@kernel.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Heiko Carstens <hca@linux.ibm.com> Fixes: f64dd462 ("ftrace: Add multi direct register/unregister interface") Signed-off-by:
Jiri Olsa <jolsa@kernel.org> Signed-off-by:
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Jiri Olsa authored
Now when we have *direct_multi interface the direct_functions hash is no longer owned just by direct_ops. It's also used by any other ftrace_ops passed to *direct_multi interface. Thus to find out that we are unregistering the last function from direct_ops, we need to check directly direct_ops's hash. Link: https://lkml.kernel.org/r/20211206182032.87248-2-jolsa@kernel.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Heiko Carstens <hca@linux.ibm.com> Fixes: f64dd462 ("ftrace: Add multi direct register/unregister interface") Signed-off-by:
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- Dec 04, 2021
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Qais Yousef authored
Commit d81ae8aa ("sched/uclamp: Fix initialization of struct uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to match the woken up task's uclamp_max when the rq is idle. The code was relying on rq->uclamp_max initialized to zero, so on first enqueue static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, enum uclamp_id clamp_id) { ... if (uc_se->value > READ_ONCE(uc_rq->value)) WRITE_ONCE(uc_rq->value, uc_se->value); } was actually resetting it. But since commit d81ae8aa changed the default to 1024, this no longer works. And since rq->uclamp_flags is also initialized to 0, neither above code path nor uclamp_idle_reset() update the rq->uclamp_max on first wake up from idle. This is only visible from first wake up(s) until the first dequeue to idle after enabling the static key. And it only matters if the uclamp_max of this task is < 1024 since only then its uclamp_max will be effectively ignored. Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to ensure uclamp_idle_reset() is called which then will update the rq uclamp_max value as expected. Fixes: d81ae8aa ("sched/uclamp: Fix initialization of struct uclamp_rq") Signed-off-by:
Qais Yousef <qais.yousef@arm.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by:
Valentin Schneider <Valentin.Schneider@arm.com> Tested-by:
Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
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Andrew Halaney authored
__setup() callbacks expect 1 for success and 0 for failure. Correct the usage here to reflect that. Fixes: 826bfeb3 ("preempt/dynamic: Support dynamic preempt with preempt= boot option") Reported-by:
Mark Rutland <mark.rutland@arm.com> Signed-off-by:
Andrew Halaney <ahalaney@redhat.com> Signed-off-by:
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- Dec 03, 2021
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Maxim Mikityanskiy authored
The first commit cited below attempts to fix the off-by-one error that appeared in some comparisons with an open range. Due to this error, arithmetically equivalent pieces of code could get different verdicts from the verifier, for example (pseudocode): // 1. Passes the verifier: if (data + 8 > data_end) return early read *(u64 *)data, i.e. [data; data+7] // 2. Rejected by the verifier (should still pass): if (data + 7 >= data_end) return early read *(u64 *)data, i.e. [data; data+7] The attempted fix, however, shifts the range by one in a wrong direction, so the bug not only remains, but also such piece of code starts failing in the verifier: // 3. Rejected by the verifier, but the check is stricter than in #1. if (data + 8 >= data_end) return early read *(u64 *)data, i.e. [data; data+7] The change performed by that fix converted an off-by-one bug into off-by-two. The second commit cited below added the BPF selftests written to ensure than code chunks like #3 are rejected, however, they should be accepted. This commit fixes the off-by-two error by adjusting new_range in the right direction and fixes the tests by changing the range into the one that should actually fail. Fixes: fb2a311a ("bpf: fix off by one for range markings with L{T, E} patterns") Fixes: b37242c7 ("bpf: add test cases to bpf selftests to cover all access tests") Signed-off-by:Maxim Mikityanskiy <maximmi@nvidia.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20211130181607.593149-1-maximmi@nvidia.com
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- Dec 02, 2021
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Kumar Kartikeya Dwivedi authored
When module registering its set is built-in, THIS_MODULE will be NULL, hence we cannot return early in case owner is NULL. Fixes: 14f267d9 ("bpf: btf: Introduce helpers for dynamic BTF set registration") Signed-off-by:
Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by:
Andrii Nakryiko <andrii@kernel.org> Acked-by:
Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211122144742.477787-3-memxor@gmail.com
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Kumar Kartikeya Dwivedi authored
Vinicius Costa Gomes reported [0] that build fails when CONFIG_DEBUG_INFO_BTF is enabled and CONFIG_BPF_SYSCALL is disabled. This leads to btf.c not being compiled, and then no symbol being present in vmlinux for the declarations in btf.h. Since BTF is not useful without enabling BPF subsystem, disallow this combination. However, theoretically disabling both now could still fail, as the symbol for kfunc_btf_id_list variables is not available. This isn't a problem as the compiler usually optimizes the whole register/unregister call, but at lower optimization levels it can fail the build in linking stage. Fix that by adding dummy variables so that modules taking address of them still work, but the whole thing is a noop. [0]: https://lore.kernel.org/bpf/20211110205418.332403-1-vinicius.gomes@intel.com Fixes: 14f267d9 ("bpf: btf: Introduce helpers for dynamic BTF set registration") Reported-by:
Vinicius Costa Gomes <vinicius.gomes@intel.com> Signed-off-by:
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Frederic Weisbecker authored
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime than the actual time. task_cputime_adjusted() snapshots utime and stime and then adjust their sum to match the scheduler maintained cputime.sum_exec_runtime. Unfortunately in nohz_full, sum_exec_runtime is only updated once per second in the worst case, causing a discrepancy against utime and stime that can be updated anytime by the reader using vtime. To fix this situation, perform an update of cputime.sum_exec_runtime when the cputime snapshot reports the task as actually running while the tick is disabled. The related overhead is then contained within the relevant situations. Reported-by:
Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com> Signed-off-by:
Frederic Weisbecker <frederic@kernel.org> Signed-off-by:
Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> Acked-by:
Phil Auld <pauld@redhat.com> Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
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Frederic Weisbecker authored
When at least one CPU runs in nohz_full mode, a dedicated timekeeper CPU is guaranteed to stay online and to never stop its tick. Meanwhile on some rare case, the dedicated timekeeper may be running with interrupts disabled for a while, such as in stop_machine. If jiffies stop being updated, a nohz_full CPU may end up endlessly programming the next tick in the past, taking the last jiffies update monotonic timestamp as a stale base, resulting in an tick storm. Here is a scenario where it matters: 0) CPU 0 is the timekeeper and CPU 1 a nohz_full CPU. 1) A stop machine callback is queued to execute somewhere. 2) CPU 0 reaches MULTI_STOP_DISABLE_IRQ while CPU 1 is still in MULTI_STOP_PREPARE. Hence CPU 0 can't do its timekeeping duty. CPU 1 can still take IRQs. 3) CPU 1 receives an IRQ which queues a timer callback one jiffy forward. 4) On IRQ exit, CPU 1 schedules the tick one jiffy forward, taking last_jiffies_update as a base. But last_jiffies_update hasn't been updated for 2 jiffies since the timekeeper has interrupts disabled. 5) clockevents_program_event(), which relies on ktime_get(), observes that the expiration is in the past and therefore programs the min delta event on the clock. 6) The tick fires immediately, goto 3) 7) Tick storm, the nohz_full CPU is drown and takes ages to reach MULTI_STOP_DISABLE_IRQ, which is the only way out of this situation. Solve this with unconditionally updating jiffies if the value is stale on nohz_full IRQ entry. IRQs and other disturbances are expected to be rare enough on nohz_full for the unconditional call to ktime_get() to actually matter. Reported-by:
Paul E. McKenney <paulmck@kernel.org> Signed-off-by:
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- Dec 01, 2021
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Masami Hiramatsu authored
The 'kprobe::data_size' is unsigned, thus it can not be negative. But if user sets it enough big number (e.g. (size_t)-8), the result of 'data_size + sizeof(struct kretprobe_instance)' becomes smaller than sizeof(struct kretprobe_instance) or zero. In result, the kretprobe_instance are allocated without enough memory, and kretprobe accesses outside of allocated memory. To avoid this issue, introduce a max limitation of the kretprobe::data_size. 4KB per instance should be OK. Link: https://lkml.kernel.org/r/163836995040.432120.10322772773821182925.stgit@devnote2 Cc: stable@vger.kernel.org Fixes: f47cd9b5 ("kprobes: kretprobe user entry-handler") Reported-by:
zhangyue <zhangyue1@kylinos.cn> Signed-off-by:
Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by:
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Chen Jun authored
Doing the command: echo 'hist:key=common_pid.execname,common_timestamp' > /sys/kernel/debug/tracing/events/xxx/trigger Triggers many kmemleak reports: unreferenced object 0xffff0000c7ea4980 (size 128): comm "bash", pid 338, jiffies 4294912626 (age 9339.324s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000f3469921>] kmem_cache_alloc_trace+0x4c0/0x6f0 [<0000000054ca40c3>] hist_trigger_elt_data_alloc+0x140/0x178 [<00000000633bd154>] tracing_map_init+0x1f8/0x268 [<000000007e814ab9>] event_hist_trigger_func+0xca0/0x1ad0 [<00000000bf8520ed>] trigger_process_regex+0xd4/0x128 [<00000000f549355a>] event_trigger_write+0x7c/0x120 [<00000000b80f898d>] vfs_write+0xc4/0x380 [<00000000823e1055>] ksys_write+0x74/0xf8 [<000000008a9374aa>] __arm64_sys_write+0x24/0x30 [<0000000087124017>] do_el0_svc+0x88/0x1c0 [<00000000efd0dcd1>] el0_svc+0x1c/0x28 [<00000000dbfba9b3>] el0_sync_handler+0x88/0xc0 [<00000000e7399680>] el0_sync+0x148/0x180 unreferenced object 0xffff0000c7ea4980 (size 128): comm "bash", pid 338, jiffies 4294912626 (age 9339.324s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000f3469921>] kmem_cache_alloc_trace+0x4c0/0x6f0 [<0000000054ca40c3>] hist_trigger_elt_data_alloc+0x140/0x178 [<00000000633bd154>] tracing_map_init+0x1f8/0x268 [<000000007e814ab9>] event_hist_trigger_func+0xca0/0x1ad0 [<00000000bf8520ed>] trigger_process_regex+0xd4/0x128 [<00000000f549355a>] event_trigger_write+0x7c/0x120 [<00000000b80f898d>] vfs_write+0xc4/0x380 [<00000000823e1055>] ksys_write+0x74/0xf8 [<000000008a9374aa>] __arm64_sys_write+0x24/0x30 [<0000000087124017>] do_el0_svc+0x88/0x1c0 [<00000000efd0dcd1>] el0_svc+0x1c/0x28 [<00000000dbfba9b3>] el0_sync_handler+0x88/0xc0 [<00000000e7399680>] el0_sync+0x148/0x180 The reason is elts->pages[i] is alloced by get_zeroed_page. and kmemleak will not scan the area alloced by get_zeroed_page. The address stored in elts->pages will be regarded as leaked. That is, the elts->pages[i] will have pointers loaded onto it as well, and without telling kmemleak about it, those pointers will look like memory without a reference. To fix this, call kmemleak_alloc to tell kmemleak to scan elts->pages[i] Link: https://lkml.kernel.org/r/20211124140801.87121-1-chenjun102@huawei.com Signed-off-by:Chen Jun <chenjun102@huawei.com> Signed-off-by:
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Steven Rostedt (VMware) authored
When comparing two strings for the "onmatch" histogram trigger, fields that are strings use string comparisons, which do not care about being signed or not. Do not fail to match two string fields if one is unsigned char array and the other is a signed char array. Link: https://lore.kernel.org/all/20211129123043.5cfd687a@gandalf.local.home/ Cc: stable@vgerk.kernel.org Cc: Tom Zanussi <zanussi@kernel.org> Cc: Yafang Shao <laoar.shao@gmail.com> Fixes: b05e89ae ("tracing: Accept different type for synthetic event fields") Reviewed-by:
Masami Hiramatsu <mhiramatsu@kernel.org> Reported-by:
Sven Schnelle <svens@linux.ibm.com> Signed-off-by:
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- Nov 27, 2021
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Steven Rostedt (VMware) authored
When creating a new event (via a module, kprobe, eprobe, etc), the descriptors that are created must add flags for pid filtering if an instance has pid filtering enabled, as the flags are used at the time the event is executed to know if pid filtering should be done or not. The "Only trace this pid" case was added, but a cut and paste error made that case checked twice, instead of checking the "Trace all but this pid" case. Link: https://lore.kernel.org/all/202111280401.qC0z99JB-lkp@intel.com/ Fixes: 6cb20650 ("tracing: Check pid filtering when creating events") Reported-by:
kernel test robot <lkp@intel.com> Signed-off-by:
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- Nov 26, 2021
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Steven Rostedt (VMware) authored
If a event is filtered by pid and a trigger that requires processing of the event to happen is a attached to the event, the discard portion does not take the pid filtering into account, and the event will then be recorded when it should not have been. Cc: stable@vger.kernel.org Fixes: 3fdaf80f ("tracing: Implement event pid filtering") Signed-off-by:
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Steven Rostedt (VMware) authored
When pid filtering is activated in an instance, all of the events trace files for that instance has the PID_FILTER flag set. This determines whether or not pid filtering needs to be done on the event, otherwise the event is executed as normal. If pid filtering is enabled when an event is created (via a dynamic event or modules), its flag is not updated to reflect the current state, and the events are not filtered properly. Cc: stable@vger.kernel.org Fixes: 3fdaf80f ("tracing: Implement event pid filtering") Signed-off-by:
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- Nov 24, 2021
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Evan Green authored
snapshot_write() is inappropriately limiting the amount of data that can be written in cases where a partial page has already been written. For example, one would expect to be able to write 1 byte, then 4095 bytes to the snapshot device, and have both of those complete fully (since now we're aligned to a page again). But what ends up happening is we write 1 byte, then 4094/4095 bytes complete successfully. The reason is that simple_write_to_buffer()'s second argument is the total size of the buffer, not the size of the buffer minus the offset. Since simple_write_to_buffer() accounts for the offset in its implementation, snapshot_write() can just pass the full page size directly down. Signed-off-by:
Evan Green <evgreen@chromium.org> Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Thomas Zeitlhofer authored
Commit 39fbef4b ("PM: hibernate: Get block device exclusively in swsusp_check()") changed the opening mode of the block device to (FMODE_READ | FMODE_EXCL). In the corresponding calls to swsusp_close(), the mode is still just FMODE_READ which triggers the warning in blkdev_flush_mapping() on resume from hibernate. So, use the mode (FMODE_READ | FMODE_EXCL) also when closing the device. Fixes: 39fbef4b ("PM: hibernate: Get block device exclusively in swsusp_check()") Signed-off-by:
Thomas Zeitlhofer <thomas.zeitlhofer+lkml@ze-it.at> Signed-off-by:
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Mark Rutland authored
To hot unplug a CPU, the idle task on that CPU calls a few layers of C code before finally leaving the kernel. When KASAN is in use, poisoned shadow is left around for each of the active stack frames, and when shadow call stacks are in use. When shadow call stacks (SCS) are in use the task's saved SCS SP is left pointing at an arbitrary point within the task's shadow call stack. When a CPU is offlined than onlined back into the kernel, this stale state can adversely affect execution. Stale KASAN shadow can alias new stackframes and result in bogus KASAN warnings. A stale SCS SP is effectively a memory leak, and prevents a portion of the shadow call stack being used. Across a number of hotplug cycles the idle task's entire shadow call stack can become unusable. We previously fixed the KASAN issue in commit: e1b77c92 ("sched/kasan: remove stale KASAN poison after hotplug") ... by removing any stale KASAN stack poison immediately prior to onlining a CPU. Subsequently in commit: f1a0a376 ("sched/core: Initialize the idle task with preemption disabled") ... the refactoring left the KASAN and SCS cleanup in one-time idle thread initialization code rather than something invoked prior to each CPU being onlined, breaking both as above. We fixed SCS (but not KASAN) in commit: 63acd42c ("sched/scs: Reset the shadow stack when idle_task_exit") ... but as this runs in the context of the idle task being offlined it's potentially fragile. To fix these consistently and more robustly, reset the SCS SP and KASAN shadow of a CPU's idle task immediately before we online that CPU in bringup_cpu(). This ensures the idle task always has a consistent state when it is running, and removes the need to so so when exiting an idle task. Whenever any thread is created, dup_task_struct() will give the task a stack which is free of KASAN shadow, and initialize the task's SCS SP, so there's no need to specially initialize either for idle thread within init_idle(), as this was only necessary to handle hotplug cycles. I've tested this on arm64 with: * gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK * clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK ... offlining and onlining CPUS with: | while true; do | for C in /sys/devices/system/cpu/cpu*/online; do | echo 0 > $C; | echo 1 > $C; | done | done Fixes: f1a0a376 ("sched/core: Initialize the idle task with preemption disabled") Reported-by:
Qian Cai <quic_qiancai@quicinc.com> Signed-off-by:
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- Nov 23, 2021
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Jiri Olsa authored
Add missing 'tu' variable initialization in the probes loop, otherwise the head 'tu' is used instead of added probes. Link: https://lkml.kernel.org/r/20211123142801.182530-1-jolsa@kernel.org Cc: stable@vger.kernel.org Fixes: 99c9a923 ("tracing/uprobe: Fix double perf_event linking on multiprobe uprobe") Acked-by:
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Marco Elver authored
syzbot reported that the warning in perf_sigtrap() fires, saying that the event's task does not match current: | WARNING: CPU: 0 PID: 9090 at kernel/events/core.c:6446 perf_pending_event+0x40d/0x4b0 kernel/events/core.c:6513 | Modules linked in: | CPU: 0 PID: 9090 Comm: syz-executor.1 Not tainted 5.15.0-syzkaller #0 | Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 | RIP: 0010:perf_sigtrap kernel/events/core.c:6446 [inline] | RIP: 0010:perf_pending_event_disable kernel/events/core.c:6470 [inline] | RIP: 0010:perf_pending_event+0x40d/0x4b0 kernel/events/core.c:6513 | ... | Call Trace: | <IRQ> | irq_work_single+0x106/0x220 kernel/irq_work.c:211 | irq_work_run_list+0x6a/0x90 kernel/irq_work.c:242 | irq_work_run+0x4f/0xd0 kernel/irq_work.c:251 | __sysvec_irq_work+0x95/0x3d0 arch/x86/kernel/irq_work.c:22 | sysvec_irq_work+0x8e/0xc0 arch/x86/kernel/irq_work.c:17 | </IRQ> | <TASK> | asm_sysvec_irq_work+0x12/0x20 arch/x86/include/asm/idtentry.h:664 | RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] | RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:194 | ... | coredump_task_exit kernel/exit.c:371 [inline] | do_exit+0x1865/0x25c0 kernel/exit.c:771 | do_group_exit+0xe7/0x290 kernel/exit.c:929 | get_signal+0x3b0/0x1ce0 kernel/signal.c:2820 | arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868 | handle_signal_work kernel/entry/common.c:148 [inline] | exit_to_user_mode_loop kernel/entry/common.c:172 [inline] | exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207 | __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] | syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300 | do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 | entry_SYSCALL_64_after_hwframe+0x44/0xae On x86 this shouldn't happen, which has arch_irq_work_raise(). The test program sets up a perf event with sigtrap set to fire on the 'sched_wakeup' tracepoint, which fired in ttwu_do_wakeup(). This happened because the 'sched_wakeup' tracepoint also takes a task argument passed on to perf_tp_event(), which is used to deliver the event to that other task. Since we cannot deliver synchronous signals to other tasks, skip an event if perf_tp_event() is targeted at another task and perf_event_attr::sigtrap is set, which will avoid ever entering perf_sigtrap() for such events. Fixes: 97ba62b2 ("perf: Add support for SIGTRAP on perf events") Reported-by:
<syzbot+663359e32ce6f1a305ad@syzkaller.appspotmail.com> Signed-off-by:
Marco Elver <elver@google.com> Signed-off-by:
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Muchun Song authored
We found that a process with 10 thousnads threads has been encountered a regression problem from Linux-v4.14 to Linux-v5.4. It is a kind of workload which will concurrently allocate lots of memory in different threads sometimes. In this case, we will see the down_read_trylock() with a high hotspot. Therefore, we suppose that rwsem has a regression at least since Linux-v5.4. In order to easily debug this problem, we write a simply benchmark to create the similar situation lile the following. ```c++ #include <sys/mman.h> #include <sys/time.h> #include <sys/resource.h> #include <sched.h> #include <cstdio> #include <cassert> #include <thread> #include <vector> #include <chrono> volatile int mutex; void trigger(int cpu, char* ptr, std::size_t sz) { cpu_set_t set; CPU_ZERO(&set); CPU_SET(cpu, &set); assert(pthread_setaffinity_np(pthread_self(), sizeof(set), &set) == 0); while (mutex); for (std::size_t i = 0; i < sz; i += 4096) { *ptr = '\0'; ptr += 4096; } } int main(int argc, char* argv[]) { std::size_t sz = 100; if (argc > 1) sz = atoi(argv[1]); auto nproc = std::thread::hardware_concurrency(); std::vector<std::thread> thr; sz <<= 30; auto* ptr = mmap(nullptr, sz, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); assert(ptr != MAP_FAILED); char* cptr = static_cast<char*>(ptr); auto run = sz / nproc; run = (run >> 12) << 12; mutex = 1; for (auto i = 0U; i < nproc; ++i) { thr.emplace_back(std::thread([i, cptr, run]() { trigger(i, cptr, run); })); cptr += run; } rusage usage_start; getrusage(RUSAGE_SELF, &usage_start); auto start = std::chrono::system_clock::now(); mutex = 0; for (auto& t : thr) t.join(); rusage usage_end; getrusage(RUSAGE_SELF, &usage_end); auto end = std::chrono::system_clock::now(); timeval utime; timeval stime; timersub(&usage_end.ru_utime, &usage_start.ru_utime, &utime); timersub(&usage_end.ru_stime, &usage_start.ru_stime, &stime); printf("usr: %ld.%06ld\n", utime.tv_sec, utime.tv_usec); printf("sys: %ld.%06ld\n", stime.tv_sec, stime.tv_usec); printf("real: %lu\n", std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()); return 0; } ``` The functionality of above program is simply which creates `nproc` threads and each of them are trying to touch memory (trigger page fault) on different CPU. Then we will see the similar profile by `perf top`. 25.55% [kernel] [k] down_read_trylock 14.78% [kernel] [k] handle_mm_fault 13.45% [kernel] [k] up_read 8.61% [kernel] [k] clear_page_erms 3.89% [kernel] [k] __do_page_fault The highest hot instruction, which accounts for about 92%, in down_read_trylock() is cmpxchg like the following. 91.89 │ lock cmpxchg %rdx,(%rdi) Sice the problem is found by migrating from Linux-v4.14 to Linux-v5.4, so we easily found that the commit ddb20d1d ("locking/rwsem: Optimize down_read_trylock()") caused the regression. The reason is that the commit assumes the rwsem is not contended at all. But it is not always true for mmap lock which could be contended with thousands threads. So most threads almost need to run at least 2 times of "cmpxchg" to acquire the lock. The overhead of atomic operation is higher than non-atomic instructions, which caused the regression. By using the above benchmark, the real executing time on a x86-64 system before and after the patch were: Before Patch After Patch # of Threads real real reduced by ------------ ------ ------ ---------- 1 65,373 65,206 ~0.0% 4 15,467 15,378 ~0.5% 40 6,214 5,528 ~11.0% For the uncontended case, the new down_read_trylock() is the same as before. For the contended cases, the new down_read_trylock() is faster than before. The more contended, the more fast. Signed-off-by:Muchun Song <songmuchun@bytedance.com> Signed-off-by:
Waiman Long <longman@redhat.com> Link: https://lore.kernel.org/r/20211118094455.9068-1-songmuchun@bytedance.com
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Waiman Long authored
There are some inconsistency in the way that the handoff bit is being handled in readers and writers that lead to a race condition. Firstly, when a queue head writer set the handoff bit, it will clear it when the writer is being killed or interrupted on its way out without acquiring the lock. That is not the case for a queue head reader. The handoff bit will simply be inherited by the next waiter. Secondly, in the out_nolock path of rwsem_down_read_slowpath(), both the waiter and handoff bits are cleared if the wait queue becomes empty. For rwsem_down_write_slowpath(), however, the handoff bit is not checked and cleared if the wait queue is empty. This can potentially make the handoff bit set with empty wait queue. Worse, the situation in rwsem_down_write_slowpath() relies on wstate, a variable set outside of the critical section containing the ->count manipulation, this leads to race condition where RWSEM_FLAG_HANDOFF can be double subtracted, corrupting ->count. To make the handoff bit handling more consistent and robust, extract out handoff bit clearing code into the new rwsem_del_waiter() helper function. Also, completely eradicate wstate; always evaluate everything inside the same critical section. The common function will only use atomic_long_andnot() to clear bits when the wait queue is empty to avoid possible race condition. If the first waiter with handoff bit set is killed or interrupted to exit the slowpath without acquiring the lock, the next waiter will inherit the handoff bit. While at it, simplify the trylock for loop in rwsem_down_write_slowpath() to make it easier to read. Fixes: 4f23dbc1 ("locking/rwsem: Implement lock handoff to prevent lock starvation") Reported-by:
Zhenhua Ma <mazhenhua@xiaomi.com> Suggested-by:
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- Nov 19, 2021
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Eric W. Biederman authored
Recently to prevent issues with SECCOMP_RET_KILL and similar signals being changed before they are delivered SA_IMMUTABLE was added. Unfortunately this broke debuggers[1][2] which reasonably expect to be able to trap synchronous SIGTRAP and SIGSEGV even when the target process is not configured to handle those signals. Add force_exit_sig and use it instead of force_fatal_sig where historically the code has directly called do_exit. This has the implementation benefits of going through the signal exit path (including generating core dumps) without the danger of allowing userspace to ignore or change these signals. This avoids userspace regressions as older kernels exited with do_exit which debuggers also can not intercept. In the future is should be possible to improve the quality of implementation of the kernel by changing some of these force_exit_sig calls to force_fatal_sig. That can be done where it matters on a case-by-case basis with careful analysis. Reported-by:
Kyle Huey <me@kylehuey.com> Reported-by:
kernel test robot <oliver.sang@intel.com> [1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com [2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020 Fixes: 00b06da2 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed") Fixes: a3616a3c ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die") Fixes: 83a1f27a ("signal/powerpc: On swapcontext failure force SIGSEGV") Fixes: 9bc508cf ("signal/s390: Use force_sigsegv in default_trap_handler") Fixes: 086ec444 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig") Fixes: c317d306 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails") Fixes: 695dd0d6 ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit") Fixes: 1fbd60df ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.") Fixes: 941edc5b ("exit/syscall_user_dispatch: Send ordinary signals on failure") Link: https://lkml.kernel.org/r/871r3dqfv8.fsf_-_@email.froward.int.ebiederm.org Reviewed-by:
Kees Cook <keescook@chromium.org> Tested-by:
Kyle Huey <khuey@kylehuey.com> Signed-off-by:
"Eric W. Biederman" <ebiederm@xmission.com>
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Eric W. Biederman authored
Recently to prevent issues with SECCOMP_RET_KILL and similar signals being changed before they are delivered SA_IMMUTABLE was added. Unfortunately this broke debuggers[1][2] which reasonably expect to be able to trap synchronous SIGTRAP and SIGSEGV even when the target process is not configured to handle those signals. Update force_sig_to_task to support both the case when we can allow the debugger to intercept and possibly ignore the signal and the case when it is not safe to let userspace know about the signal until the process has exited. Suggested-by:
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- Nov 18, 2021
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Nikita Yushchenko authored
If trace_seq becomes full, trace_seq_vprintf() no longer consumes arguments from va_list, making va_list out of sync with format processing by trace_check_vprintf(). This causes va_arg() in trace_check_vprintf() to return wrong positional argument, which results into a WARN_ON_ONCE() hit. ftrace_stress_test from LTP triggers this situation. Fix it by explicitly avoiding further use if va_list at the point when it's consistency can no longer be guaranteed. Link: https://lkml.kernel.org/r/20211118145516.13219-1-nikita.yushchenko@virtuozzo.com Signed-off-by:
Nikita Yushchenko <nikita.yushchenko@virtuozzo.com> Signed-off-by:
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Kees Cook authored
In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memset(), avoid intentionally writing across neighboring fields. Use memset_startat() to avoid confusing memset() about writing beyond the target struct member. Link: https://lkml.kernel.org/r/20211118202217.1285588-1-keescook@chromium.org Signed-off-by:
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Kalesh Singh authored
Calling destroy_hist_field() on an expression will recursively free any operands associated with the expression. If during expression parsing the operands of the expression are already set when an error is encountered, there is no need to explicity free the operands. Doing so will result in destroy_hist_field() being called twice for the operands and lead to a use-after-free (UAF) error. If the operands are associated with the expression, only call destroy_hist_field() on the expression since the operands will be recursively freed. Link: https://lore.kernel.org/all/CAHk-=wgcrEbFgkw9720H3tW-AhHOoEKhYwZinYJw4FpzSaJ6_Q@mail.gmail.com/ Link: https://lkml.kernel.org/r/20211118011542.1420131-1-kaleshsingh@google.com Suggested-by:
Kalesh Singh <kaleshsingh@google.com> Fixes: 8b5d46fd ("tracing/histogram: Optimize division by constants") Reported-by:
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- Nov 15, 2021
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Daniel Borkmann authored
Commit a23740ec ("bpf: Track contents of read-only maps as scalars") is checking whether maps are read-only both from BPF program side and user space side, and then, given their content is constant, reading out their data via map->ops->map_direct_value_addr() which is then subsequently used as known scalar value for the register, that is, it is marked as __mark_reg_known() with the read value at verification time. Before a23740ec, the register content was marked as an unknown scalar so the verifier could not make any assumptions about the map content. The current implementation however is prone to a TOCTOU race, meaning, the value read as known scalar for the register is not guaranteed to be exactly the same at a later point when the program is executed, and as such, the prior made assumptions of the verifier with regards to the program will be invalid which can cause issues such as OOB access, etc. While the BPF_F_RDONLY_PROG map flag is always fixed and required to be specified at map creation time, the map->frozen property is initially set to false for the map given the map value needs to be populated, e.g. for global data sections. Once complete, the loader "freezes" the map from user space such that no subsequent updates/deletes are possible anymore. For the rest of the lifetime of the map, this freeze one-time trigger cannot be undone anymore after a successful BPF_MAP_FREEZE cmd return. Meaning, any new BPF_* cmd calls which would update/delete map entries will be rejected with -EPERM since map_get_sys_perms() removes the FMODE_CAN_WRITE permission. This also means that pending update/delete map entries must still complete before this guarantee is given. This corner case is not an issue for loaders since they create and prepare such program private map in successive steps. However, a malicious user is able to trigger this TOCTOU race in two different ways: i) via userfaultfd, and ii) via batched updates. For i) userfaultfd is used to expand the competition interval, so that map_update_elem() can modify the contents of the map after map_freeze() and bpf_prog_load() were executed. This works, because userfaultfd halts the parallel thread which triggered a map_update_elem() at the time where we copy key/value from the user buffer and this already passed the FMODE_CAN_WRITE capability test given at that time the map was not "frozen". Then, the main thread performs the map_freeze() and bpf_prog_load(), and once that had completed successfully, the other thread is woken up to complete the pending map_update_elem() which then changes the map content. For ii) the idea of the batched update is similar, meaning, when there are a large number of updates to be processed, it can increase the competition interval between the two. It is therefore possible in practice to modify the contents of the map after executing map_freeze() and bpf_prog_load(). One way to fix both i) and ii) at the same time is to expand the use of the map's map->writecnt. The latter was introduced in fc970227 ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY") and further refined in 1f6cb19b ("bpf: Prevent re-mmap()'ing BPF map as writable for initially r/o mapping") with the rationale to make a writable mmap()'ing of a map mutually exclusive with read-only freezing. The counter indicates writable mmap() mappings and then prevents/fails the freeze operation. Its semantics can be expanded beyond just mmap() by generally indicating ongoing write phases. This would essentially span any parallel regular and batched flavor of update/delete operation and then also have map_freeze() fail with -EBUSY. For the check_mem_access() in the verifier we expand upon the bpf_map_is_rdonly() check ensuring that all last pending writes have completed via bpf_map_write_active() test. Once the map->frozen is set and bpf_map_write_active() indicates a map->writecnt of 0 only then we are really guaranteed to use the map's data as known constants. For map->frozen being set and pending writes in process of still being completed we fall back to marking that register as unknown scalar so we don't end up making assumptions about it. With this, both TOCTOU reproducers from i) and ii) are fixed. Note that the map->writecnt has been converted into a atomic64 in the fix in order to avoid a double freeze_mutex mutex_{un,}lock() pair when updating map->writecnt in the various map update/delete BPF_* cmd flavors. Spanning the freeze_mutex over entire map update/delete operations in syscall side would not be possible due to then causing everything to be serialized. Similarly, something like synchronize_rcu() after setting map->frozen to wait for update/deletes to complete is not possible either since it would also have to span the user copy which can sleep. On the libbpf side, this won't break d66562fb ("libbpf: Add BPF object skeleton support") as the anonymous mmap()-ed "map initialization image" is remapped as a BPF map-backed mmap()-ed memory where for .rodata it's non-writable. Fixes: a23740ec ("bpf: Track contents of read-only maps as scalars") Reported-by:
<w1tcher.bupt@gmail.com> Signed-off-by:
Alexei Starovoitov <ast@kernel.org>
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Dmitrii Banshchikov authored
Use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in tracing progs may result in locking issues. bpf_ktime_get_coarse_ns() uses ktime_get_coarse_ns() time accessor that isn't safe for any context: ====================================================== WARNING: possible circular locking dependency detected 5.15.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/14877 is trying to acquire lock: ffffffff8cb30008 (tk_core.seq.seqcount){----}-{0:0}, at: ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255 but task is already holding lock: ffffffff90dbf200 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_deactivate+0x61/0x400 lib/debugobjects.c:735 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&obj_hash[i].lock){-.-.}-{2:2}: lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162 __debug_object_init+0xd9/0x1860 lib/debugobjects.c:569 debug_hrtimer_init kernel/time/hrtimer.c:414 [inline] debug_init kernel/time/hrtimer.c:468 [inline] hrtimer_init+0x20/0x40 kernel/time/hrtimer.c:1592 ntp_init_cmos_sync kernel/time/ntp.c:676 [inline] ntp_init+0xa1/0xad kernel/time/ntp.c:1095 timekeeping_init+0x512/0x6bf kernel/time/timekeeping.c:1639 start_kernel+0x267/0x56e init/main.c:1030 secondary_startup_64_no_verify+0xb1/0xbb -> #0 (tk_core.seq.seqcount){----}-{0:0}: check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain+0x1dfb/0x8240 kernel/locking/lockdep.c:3789 __lock_acquire+0x1382/0x2b00 kernel/locking/lockdep.c:5015 lock_acquire+0x19f/0x4d0 kernel/locking/lockdep.c:5625 seqcount_lockdep_reader_access+0xfe/0x230 include/linux/seqlock.h:103 ktime_get_coarse_ts64+0x25/0x110 kernel/time/timekeeping.c:2255 ktime_get_coarse include/linux/timekeeping.h:120 [inline] ktime_get_coarse_ns include/linux/timekeeping.h:126 [inline] ____bpf_ktime_get_coarse_ns kernel/bpf/helpers.c:173 [inline] bpf_ktime_get_coarse_ns+0x7e/0x130 kernel/bpf/helpers.c:171 bpf_prog_a99735ebafdda2f1+0x10/0xb50 bpf_dispatcher_nop_func include/linux/bpf.h:721 [inline] __bpf_prog_run include/linux/filter.h:626 [inline] bpf_prog_run include/linux/filter.h:633 [inline] BPF_PROG_RUN_ARRAY include/linux/bpf.h:1294 [inline] trace_call_bpf+0x2cf/0x5d0 kernel/trace/bpf_trace.c:127 perf_trace_run_bpf_submit+0x7b/0x1d0 kernel/events/core.c:9708 perf_trace_lock+0x37c/0x440 include/trace/events/lock.h:39 trace_lock_release+0x128/0x150 include/trace/events/lock.h:58 lock_release+0x82/0x810 kernel/locking/lockdep.c:5636 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline] _raw_spin_unlock_irqrestore+0x75/0x130 kernel/locking/spinlock.c:194 debug_hrtimer_deactivate kernel/time/hrtimer.c:425 [inline] debug_deactivate kernel/time/hrtimer.c:481 [inline] __run_hrtimer kernel/time/hrtimer.c:1653 [inline] __hrtimer_run_queues+0x2f9/0xa60 kernel/time/hrtimer.c:1749 hrtimer_interrupt+0x3b3/0x1040 kernel/time/hrtimer.c:1811 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline] __sysvec_apic_timer_interrupt+0xf9/0x270 arch/x86/kernel/apic/apic.c:1103 sysvec_apic_timer_interrupt+0x8c/0xb0 arch/x86/kernel/apic/apic.c:1097 asm_sysvec_apic_timer_interrupt+0x12/0x20 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] _raw_spin_unlock_irqrestore+0xd4/0x130 kernel/locking/spinlock.c:194 try_to_wake_up+0x702/0xd20 kernel/sched/core.c:4118 wake_up_process kernel/sched/core.c:4200 [inline] wake_up_q+0x9a/0xf0 kernel/sched/core.c:953 futex_wake+0x50f/0x5b0 kernel/futex/waitwake.c:184 do_futex+0x367/0x560 kernel/futex/syscalls.c:127 __do_sys_futex kernel/futex/syscalls.c:199 [inline] __se_sys_futex+0x401/0x4b0 kernel/futex/syscalls.c:180 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae There is a possible deadlock with bpf_timer_* set of helpers: hrtimer_start() lock_base(); trace_hrtimer...() perf_event() bpf_run() bpf_timer_start() hrtimer_start() lock_base() <- DEADLOCK Forbid use of bpf_ktime_get_coarse_ns() and bpf_timer_* helpers in BPF_PROG_TYPE_KPROBE, BPF_PROG_TYPE_TRACEPOINT, BPF_PROG_TYPE_PERF_EVENT and BPF_PROG_TYPE_RAW_TRACEPOINT prog types. Fixes: d0551261 ("bpf: Add bpf_ktime_get_coarse_ns helper") Fixes: b00628b1 ("bpf: Introduce bpf timers.") Reported-by:<syzbot+43fd005b5a1b4d10781e@syzkaller.appspotmail.com> Signed-off-by:
Dmitrii Banshchikov <me@ubique.spb.ru> Signed-off-by:
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- Nov 14, 2021
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Steven Rostedt (VMware) authored
The string copies to the histogram storage has a max size of 256 bytes (defined by MAX_FILTER_STR_VAL). Only the string size of the event field needs to be copied to the event storage, but no more than what is in the event storage. Although nothing should be bigger than 256 bytes, there's no protection against overwriting of the storage if one day there is. Copy no more than the destination size, and enforce it. Also had to turn MAX_FILTER_STR_VAL into an unsigned int, to keep the min() comparison of the string sizes of comparable types. Link: https://lore.kernel.org/all/CAHk-=wjREUihCGrtRBwfX47y_KrLCGjiq3t6QtoNJpmVrAEb1w@mail.gmail.com/ Link: https://lkml.kernel.org/r/20211114132834.183429a4@rorschach.local.home Cc: Ingo Molnar <mingo@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tom Zanussi <zanussi@kernel.org> Reported-by:
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- Nov 12, 2021
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Kalesh Singh authored
If a binary operation is detected while parsing an expression string, the operand strings are deduced by splitting the experssion string at the position of the detected binary operator. Both operand strings are sub-strings (can be empty string) of the expression string but will never be NULL. Currently a NULL check is used for missing operands, fix this by checking for empty strings instead. Link: https://lkml.kernel.org/r/20211112191324.1302505-1-kaleshsingh@google.com Signed-off-by:
Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by:
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Masami Hiramatsu authored
Do not copy the fixed-size char array field of the events over the field size. The histogram treats char array as a string and there are 2 types of char array in the event, fixed-size and dynamic string. The dynamic string (__data_loc) field must be null terminated, but the fixed-size char array field may not be null terminated (not a string, but just a data). In that case, histogram can copy the data after the field. This uses the original field size for fixed-size char array field to restrict the histogram not to access over the original field size. Link: https://lkml.kernel.org/r/163673292822.195747.3696966210526410250.stgit@devnote2 Fixes: 02205a67 (tracing: Add support for 'field variables') Signed-off-by:
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Alexei Starovoitov authored
Introduction of map_uid made two lookups from outer map to be distinct. That distinction is only necessary when inner map has an embedded timer. Otherwise it will make the verifier state pruning to be conservative which will cause complex programs to hit 1M insn_processed limit. Tighten map_uid logic to apply to inner maps with timers only. Fixes: 3e8ce298 ("bpf: Prevent pointer mismatch in bpf_timer_init.") Reported-by:
Lorenz Bauer <lmb@cloudflare.com> Signed-off-by:
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Daniel Bristot de Oliveira authored
Make the struct list_head osnoise_instances definition static. Link: https://lore.kernel.org/all/202111120052.ZuikQSJi-lkp@intel.com/ Link: https://lkml.kernel.org/r/d001f0eeac66e2b2eeec7d2a15e9e7abede0453a.1636667971.git.bristot@kernel.org Cc: Ingo Molnar <mingo@redhat.com> Fixes: dae18134 ("tracing/osnoise: Support a list of trace_array *tr") Reported-by:
Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by:
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- Nov 11, 2021
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Greg Thelen authored
PEBS PERF_SAMPLE_PHYS_ADDR events use perf_virt_to_phys() to convert PMU sampled virtual addresses to physical using get_user_page_fast_only() and page_to_phys(). Some get_user_page_fast_only() error cases return false, indicating no page reference, but still initialize the output page pointer with an unreferenced page. In these error cases perf_virt_to_phys() calls put_page(). This causes page reference count underflow, which can lead to unintentional page sharing. Fix perf_virt_to_phys() to only put_page() if get_user_page_fast_only() returns a referenced page. Fixes: fc7ce9c7 ("perf/core, x86: Add PERF_SAMPLE_PHYS_ADDR") Signed-off-by:
Greg Thelen <gthelen@google.com> Signed-off-by:
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Valentin Schneider authored
Commit c597bfdd ("sched: Provide Kconfig support for default dynamic preempt mode") changed the selectable config names for the preemption model. This means a config file must now select CONFIG_PREEMPT_BEHAVIOUR=y rather than CONFIG_PREEMPT=y to get a preemptible kernel. This means all arch config files would need to be updated - right now they'll all end up with the default CONFIG_PREEMPT_NONE_BEHAVIOUR. Rather than touch a good hundred of config files, restore usage of CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure: o The build-time preemption model when !PREEMPT_DYNAMIC o The default boot-time preemption model when PREEMPT_DYNAMIC Add siblings of those configs with the _BUILD suffix to unconditionally designate the build-time preemption model (PREEMPT_DYNAMIC is built with the "highest" preemption model it supports, aka PREEMPT). Downstream configs should by now all be depending / selected by CONFIG_PREEMPTION rather than CONFIG_...
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Mathias Krause authored
Kevin is reporting crashes which point to a use-after-free of a cfs_rq in update_blocked_averages(). Initial debugging revealed that we've live cfs_rq's (on_list=1) in an about to be kfree()'d task group in free_fair_sched_group(). However, it was unclear how that can happen. His kernel config happened to lead to a layout of struct sched_entity that put the 'my_q' member directly into the middle of the object which makes it incidentally overlap with SLUB's freelist pointer. That, in combination with SLAB_FREELIST_HARDENED's freelist pointer mangling, leads to a reliable access violation in form of a #GP which made the UAF fail fast. Michal seems to have run into the same issue[1]. He already correctly diagnosed that commit a7b359fc ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") is causing the preconditions for the UAF to happen by re-adding cfs_rq's also to task groups that have no more running tasks, i.e. also to dead ones. His analysis, however, misses the real root cause and it cannot be seen from the crash backtrace only, as the real offender is tg_unthrottle_up() getting called via sched_cfs_period_timer() via the timer interrupt at an inconvenient time. When unregister_fair_sched_group() unlinks all cfs_rq's from the dying task group, it doesn't protect itself from getting interrupted. If the timer interrupt triggers while we iterate over all CPUs or after unregister_fair_sched_group() has finished but prior to unlinking the task group, sched_cfs_period_timer() will execute and walk the list of task groups, trying to unthrottle cfs_rq's, i.e. re-add them to the dying task group. These will later -- in free_fair_sched_group() -- be kfree()'ed while still being linked, leading to the fireworks Kevin and Michal are seeing. To fix this race, ensure the dying task group gets unlinked first. However, simply switching the order of unregistering and unlinking the task group isn't sufficient, as concurrent RCU walkers might still see it, as can be seen below: CPU1: CPU2: : timer IRQ: : do_sched_cfs_period_timer(): : : : distribute_cfs_runtime(): : rcu_read_lock(); : : : unthrottle_cfs_rq(): sched_offline_group(): : : walk_tg_tree_from(…,tg_unthrottle_up,…): list_del_rcu(&tg->list); : (1) : list_for_each_entry_rcu(child, &parent->children, siblings) : : (2) list_del_rcu(&tg->siblings); : : tg_unthrottle_up(): unregister_fair_sched_group(): struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; : : list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); : : : : if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running) (3) : list_add_leaf_cfs_rq(cfs_rq); : : : : : : : : : : (4) : rcu_read_unlock(); CPU 2 walks the task group list in parallel to sched_offline_group(), specifically, it'll read the soon to be unlinked task group entry at (1). Unlinking it on CPU 1 at (2) therefore won't prevent CPU 2 from still passing it on to tg_unthrottle_up(). CPU 1 now tries to unlink all cfs_rq's via list_del_leaf_cfs_rq() in unregister_fair_sched_group(). Meanwhile CPU 2 will re-add some of these at (3), which is the cause of the UAF later on. To prevent this additional race from happening, we need to wait until walk_tg_tree_from() has finished traversing the task groups, i.e. after the RCU read critical section ends in (4). Afterwards we're safe to call unregister_fair_sched_group(), as each new walk won't see the dying task group any more. On top of that, we need to wait yet another RCU grace period after unregister_fair_sched_group() to ensure print_cfs_stats(), which might run concurrently, always sees valid objects, i.e. not already free'd ones. This patch survives Michal's reproducer[2] for 8h+ now, which used to trigger within minutes before. [1] https://lore.kernel.org/lkml/20211011172236.11223-1-mkoutny@suse.com/ [2] https://lore.kernel.org/lkml/20211102160228.GA57072@blackbody.suse.cz/ Fixes: a7b359fc ("sched/fair: Correctly insert cfs_rq's to list on unthrottle") [peterz: shuffle code around a bit] Reported-by:
Kevin Tanguy <kevin.tanguy@corp.ovh.com> Signed-off-by:
Mathias Krause <minipli@grsecurity.net> Signed-off-by:
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