Marco Elver 6c605f8371 perf: Fix data race between pin_count increment/decrement ...

KCSAN reports a data race between increment and decrement of pin_count:

  write to 0xffff888237c2d4e0 of 4 bytes by task 15740 on cpu 1:
   find_get_context		kernel/events/core.c:4617
   __do_sys_perf_event_open	kernel/events/core.c:12097 [inline]
   __se_sys_perf_event_open	kernel/events/core.c:11933
   ...
  read to 0xffff888237c2d4e0 of 4 bytes by task 15743 on cpu 0:
   perf_unpin_context		kernel/events/core.c:1525 [inline]
   __do_sys_perf_event_open	kernel/events/core.c:12328 [inline]
   __se_sys_perf_event_open	kernel/events/core.c:11933
   ...

Because neither read-modify-write here is atomic, this can lead to one
of the operations being lost, resulting in an inconsistent pin_count.
Fix it by adding the missing locking in the CPU-event case.

Fixes: fe4b04fa31 ("perf: Cure task_oncpu_function_call() races")
Reported-by: [email protected]
Signed-off-by: Marco Elver <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

2021-05-31 10:14:51 +02:00

..

callchain.c

uaccess: add force_uaccess_{begin,end} helpers

2020-08-12 10:57:59 -07:00

core.c

perf: Fix data race between pin_count increment/decrement

2021-05-31 10:14:51 +02:00

hw_breakpoint.c

powerpc/watchpoint: Don't allow concurrent perf and ptrace events

2020-05-19 00:14:45 +10:00

internal.h

perf: Optimize get_recursion_context()

2020-11-09 18:12:34 +01:00

Makefile

…

ring_buffer.c

perf: Cap allocation order at aux_watermark

2021-04-16 16:32:39 +02:00

uprobes.c

kernel: delete repeated words in comments

2021-02-26 09:41:03 -08:00