KCSAN: data-race in dnotify_flush / pid_update_inode

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c1c7521f 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=135914af600000
kernel config: https://syzkaller.appspot.com/x/.config?x=c0906aa620713d80
dashboard link: https://syzkaller.appspot.com/bug?extid=5cf7401a38c3b93ddcef
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [adob...@gmail.com ak...@linux-foundation.org
ca...@schaufler-ca.com chri...@brauner.io kees...@chromium.org
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+5cf740...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dnotify_flush / pid_update_inode

write to 0xffff8881244e75a8 of 2 bytes by task 7503 on cpu 1:
pid_update_inode+0x51/0x70 fs/proc/base.c:1820
pid_revalidate+0x91/0xd0 fs/proc/base.c:1841
d_revalidate fs/namei.c:765 [inline]
d_revalidate fs/namei.c:762 [inline]
lookup_fast+0x685/0x7e0 fs/namei.c:1618
do_last fs/namei.c:3282 [inline]
path_openat+0x2ac/0x3530 fs/namei.c:3533
do_filp_open+0x11e/0x1b0 fs/namei.c:3563
do_sys_open+0x3b3/0x4f0 fs/open.c:1089
__do_sys_open fs/open.c:1107 [inline]
__se_sys_open fs/open.c:1102 [inline]
__x64_sys_open+0x55/0x70 fs/open.c:1102
do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881244e75a8 of 2 bytes by task 7494 on cpu 0:
dnotify_flush+0x3a/0x210 fs/notify/dnotify/dnotify.c:150
filp_close+0xd5/0x120 fs/open.c:1169
__close_fd+0xef/0x140 fs/file.c:636
__do_sys_close fs/open.c:1185 [inline]
__se_sys_close fs/open.c:1183 [inline]
__x64_sys_close+0x49/0xb0 fs/open.c:1183
do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7494 Comm: ps Not tainted 5.3.0+ #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.