lkml.org 
[lkml]   [2023]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 6.1.y] perf/core: Fix possible deadlock in sys_perf_event_open()
On Thu, Sep 07, 2023 at 12:38:21AM +0800, 李棒(伯兮) wrote:
> In certain scenarios, gctx and ctx may be equal in the
> __perf_event_ctx_lock_double() function, resulting in a deadlock.
>
> Thread 1, thread 2 and thread 3 belong to the same process, and the
> process number is assumed to be M. The deadlock scenario is as follows:
>
> 1) Thread 1 creates a pure software group through the system call
> sys_perf_event_open() and returns an fd, assuming the value of fd is N.
> The parameters of sys_perf_event_open() are as follows.
>
> For example:
> perf_event_attr.type = PERF_TYPE_SOFTWARE;
> pid = M;
> cpu = 0;
> group_fd = -1;
> flags = 0;
> N = sys_perf_event_open(&perf_event_attr, pid, cpu, group_fd, flags);
>
> 2) Thread 2 and thread 3 call the perf_event_open() function concurrently
> with the same parameters on a different cpu. And use the fd generated
> by thread 1 as group_fd. The parameters of sys_perf_event_open() are
> as follows.
>
> For example:
> perf_event_attr.type = PERF_TYPE_HARDWARE;
> pid = M;
> cpu = 0;
> group_fd = N;
> flags = 0;
> sys_perf_event_open(&perf_event_attr, pid, cpu, group_fd, flags);
>
> 3) In the __perf_event_ctx_lock_double function, assuming that thread 2
> successfully acquires gctx->mutex and ctx->mutex first, thread 3 will
> wait here. At the same time, thread 2 will move the pure software gruop
> to the hardware context and change group_leader->ctx to the hardware
> context.
>
> 4) When thread 2 releases gctx->mutex and ctx->mutex, thread 3 acquires
> gctx->mutex and ctx->mutex. And find that group_leader->ctx != gctx,
> then reacquires gctx. At this time, gctx is equal to the ctx of thread
> 3, triggering a deadlock.
>
> Fixes: 321027c1fe77 ("perf/core: Fix concurrent sys_perf_event_open() vs. 'move_group' race")
> Signed-off-by: Bang Li <libang.li@antgroup.com>
> ---
> kernel/events/core.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

\
 
 \ /
  Last update: 2023-09-06 22:02    [W:0.037 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site