mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-10-03 23:58:05 +00:00
Code Issues Releases Wiki Activity

- A single data race fix on the perf event cleanup path to avoid endless

Browse source 
loops due to insufficient locking
 -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCgAdFiEEzv7L6UO9uDPlPSfHEsHwGGHeVUoFAmLTu80ACgkQEsHwGGHe
 VUrophAApPj8K9M6+JLeVKNocQMA+1XhWL/HRVmabI+1TpxO4/663wcbbUI04Z5e
 51dGvvCBK413duoDUAn8tYAPjQStTrwqAS/toHcaSj+dDPHzZDd3M/Gn68SRy08d
 if26OjsXIGTZoHsCYJx0y01m9XHY4ZhVTtonsc3jZCmb/b8/feSBZcMtw+tASDAw
 8m/P9rHfzVlfBYmZnyf2NH24NTVcHgoQUGobDo16ve1CTvH8d4jEr+YPsNLTYN+P
 4cUslnvRG4HhC/u8namO8CbQVuXicyJBVdVBtfUJ0+IKojie7zCkVUOIPv+mWgQ7
 r1XE2MPSeFQRa0IptiA0vIXQCgs9BRj6cBzgo2f3Y0QjU0GGKLTcIKrILv95aej7
 X12+uNLKfnkYU4vuyG4o4AnXh047YxgfWLSQ569c/hHKuw8klTQkh0PbJEs6Epn0
 21dU+9/p66ZPTCXXjEDDNsMHeVY00+lkdEOu9YzNzMUfR5Fo+zbAN7X9jiDAQDqc
 D9IdDeEmhdmrEKNOkankMTBF1tG1XiU5zWerREeMHRMKpJhxC5X1BGIDpuEq1PJD
 xa7uAPvc0O6WmNfVvXaJ2GFPzx8oq9inlocNk/0I2ZJxgkGFqKCYUZQI0AdtzPAj
 dHx66z09uXMQN+ecXwf5pF1QS/R6BEajOaUhBEFPUZ21pkEl12c=
 =/ETy
 -----END PGP SIGNATURE-----

Merge tag 'perf_urgent_for_v5.19_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fix from Borislav Petkov:

 - A single data race fix on the perf event cleanup path to avoid
   endless loops due to insufficient locking

* tag 'perf_urgent_for_v5.19_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Fix data race between perf_event_set_output() and perf_mmap_close()
This commit is contained in:
Linus Torvalds 2022-07-17 08:34:02 -07:00
commit 2b18593e4b
1 changed files with 31 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

45
kernel/events/core.c
View file

@ -6253,10 +6253,10 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (!atomic_inc_not_zero(&event->rb->mmap_count)) {
/*
* Raced against perf_mmap_close() through
* perf_event_set_output(). Try again, hope for better
* luck.
* Raced against perf_mmap_close(); remove the
* event and try again.
*/
ring_buffer_attach(event, NULL);
mutex_unlock(&event->mmap_mutex);
goto again;
}
@ -11825,14 +11825,25 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
goto out;
}
static void mutex_lock_double(struct mutex *a, struct mutex *b)
{
if (b < a)
swap(a, b);
mutex_lock(a);
mutex_lock_nested(b, SINGLE_DEPTH_NESTING);
}
static int
perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
{
struct perf_buffer *rb = NULL;
int ret = -EINVAL;
if (!output_event)
if (!output_event) {
mutex_lock(&event->mmap_mutex);
goto set;
}
/* don't allow circular references */
if (event == output_event)
@ -11870,8 +11881,15 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
event->pmu != output_event->pmu)
goto out;
/*
* Hold both mmap_mutex to serialize against perf_mmap_close(). Since
* output_event is already on rb->event_list, and the list iteration
* restarts after every removal, it is guaranteed this new event is
* observed *OR* if output_event is already removed, it's guaranteed we
* observe !rb->mmap_count.
*/
mutex_lock_double(&event->mmap_mutex, &output_event->mmap_mutex);
set:
mutex_lock(&event->mmap_mutex);
/* Can't redirect output if we've got an active mmap() */
if (atomic_read(&event->mmap_count))
goto unlock;
@ -11881,6 +11899,12 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
rb = ring_buffer_get(output_event);
if (!rb)
goto unlock;
/* did we race against perf_mmap_close() */
if (!atomic_read(&rb->mmap_count)) {
ring_buffer_put(rb);
goto unlock;
}
}
ring_buffer_attach(event, rb);
@ -11888,20 +11912,13 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
ret = 0;
unlock:
mutex_unlock(&event->mmap_mutex);
if (output_event)
mutex_unlock(&output_event->mmap_mutex);
out:
return ret;
}
static void mutex_lock_double(struct mutex *a, struct mutex *b)
{
if (b < a)
swap(a, b);
mutex_lock(a);
mutex_lock_nested(b, SINGLE_DEPTH_NESTING);
}
static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
{
bool nmi_safe = false;