KCSAN: data-race in perf_event_update_userpage / perf_event_update_userpage

KCSAN: data-race in perf_event_update_userpage / perf_event_update_userpage

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    05f22368 x86, kcsan: Enable KCSAN for x86
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=157a35f8e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=3d30a087bef7b887dd14
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3d30a087bef7b887dd14@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in perf_event_update_userpage /  
perf_event_update_userpage

write to 0xffff88812403c00c of 4 bytes by task 12674 on cpu 1:
  perf_event_update_userpage+0x157/0x340 kernel/events/core.c:5405
  cpu_clock_event_add+0x3d/0x60 kernel/events/core.c:9672
  event_sched_in.isra.0.part.0+0x1d5/0x560 kernel/events/core.c:2367
  event_sched_in kernel/events/core.c:2339 [inline]
  group_sched_in+0xd1/0x2c0 kernel/events/core.c:2403
  flexible_sched_in kernel/events/core.c:3418 [inline]
  flexible_sched_in+0x399/0x540 kernel/events/core.c:3407
  visit_groups_merge+0x1d9/0x320 kernel/events/core.c:3366
  ctx_flexible_sched_in kernel/events/core.c:3455 [inline]
  ctx_sched_in+0x1b4/0x360 kernel/events/core.c:3500
  perf_event_sched_in+0x77/0xb0 kernel/events/core.c:2512
  perf_event_context_sched_in kernel/events/core.c:3540 [inline]
  __perf_event_task_sched_in+0x354/0x390 kernel/events/core.c:3579
  perf_event_task_sched_in include/linux/perf_event.h:1150 [inline]
  finish_task_switch+0x108/0x260 kernel/sched/core.c:3221
  context_switch kernel/sched/core.c:3387 [inline]
  __schedule+0x319/0x640 kernel/sched/core.c:4069
  schedule+0x47/0xd0 kernel/sched/core.c:4136
  freezable_schedule include/linux/freezer.h:172 [inline]
  futex_wait_queue_me+0x18d/0x290 kernel/futex.c:2627
  futex_wait+0x19b/0x3f0 kernel/futex.c:2733

write to 0xffff88812403c00c of 4 bytes by task 12673 on cpu 0:
  perf_event_update_userpage+0x157/0x340 kernel/events/core.c:5405
  perf_mmap+0xe00/0xeb0 kernel/events/core.c:5875
  call_mmap include/linux/fs.h:1900 [inline]
  mmap_region+0x83c/0xd50 mm/mmap.c:1806
  do_mmap+0x6d4/0xba0 mm/mmap.c:1577
  do_mmap_pgoff include/linux/mm.h:2353 [inline]
  vm_mmap_pgoff+0x12d/0x190 mm/util.c:496
  ksys_mmap_pgoff+0x2d8/0x420 mm/mmap.c:1629
  __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
  __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
  __x64_sys_mmap+0x91/0xc0 arch/x86/kernel/sys_x86_64.c:91
  do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12673 Comm: syz-executor.0 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
==================================================================


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