KCSAN: data-race in futex_wait_queue_me / task_dump_owner

[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=11030760e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=675eedff380a85646772
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [adob...@gmail.com ak...@linux-foundation.org
ca...@schaufler-ca.com chri...@brauner.io gu...@fb.com
kent.ov...@gmail.com khleb...@yandex-team.ru
linux-...@vger.kernel.org linux-...@vger.kernel.org mho...@suse.com
shak...@google.com tg...@linutronix.de el...@google.com]

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+675eed...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in futex_wait_queue_me / task_dump_owner

read to 0xffff888121a8a124 of 4 bytes by task 11100 on cpu 1:
task_dump_owner+0x43/0x260 fs/proc/base.c:1698
pid_update_inode+0x3c/0x70 fs/proc/base.c:1818
pid_revalidate+0x91/0xd0 fs/proc/base.c:1841
d_revalidate fs/namei.c:758 [inline]
d_revalidate fs/namei.c:755 [inline]
lookup_fast+0x6f2/0x700 fs/namei.c:1607
walk_component+0x6d/0xe80 fs/namei.c:1796
link_path_walk.part.0+0x354/0xa90 fs/namei.c:2128
link_path_walk fs/namei.c:2062 [inline]
path_openat+0x14f/0x36e0 fs/namei.c:3524
do_filp_open+0x11e/0x1b0 fs/namei.c:3555
do_sys_open+0x3b3/0x4f0 fs/open.c:1097
__do_sys_open fs/open.c:1115 [inline]
__se_sys_open fs/open.c:1110 [inline]
__x64_sys_open+0x55/0x70 fs/open.c:1110
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888121a8a124 of 4 bytes by task 11095 on cpu 0:
freezer_do_not_count include/linux/freezer.h:109 [inline]
freezable_schedule include/linux/freezer.h:171 [inline]
futex_wait_queue_me+0x17d/0x290 kernel/futex.c:2627
futex_wait+0x19b/0x3f0 kernel/futex.c:2733
do_futex+0xe9/0x18d0 kernel/futex.c:3644
__do_sys_futex kernel/futex.c:3705 [inline]
__se_sys_futex kernel/futex.c:3673 [inline]
__x64_sys_futex+0x2cd/0x3f0 kernel/futex.c:3673
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: 11095 Comm: syz-executor.4 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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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.