KCSAN: data-race in fsnotify / fsnotify_clear_marks_by_group

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 34816d20 Merge tag 'gfs2-v5.10-rc5-fixes' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=134426bb500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=9448815a71797389684a
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [amir...@gmail.com ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+944881...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fsnotify / fsnotify_clear_marks_by_group

write to 0xffff8881448461ac of 4 bytes by task 22788 on cpu 0:
fsnotify_free_mark fs/notify/mark.c:418 [inline]
fsnotify_clear_marks_by_group+0x2fb/0x3e0 fs/notify/mark.c:763
fsnotify_destroy_group+0x51/0x170 fs/notify/group.c:61
fanotify_release+0x2c5/0x2e0 fs/notify/fanotify/fanotify_user.c:623
__fput+0x243/0x4d0 fs/file_table.c:281
____fput+0x11/0x20 fs/file_table.c:314
task_work_run+0x8e/0x110 kernel/task_work.c:151
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881448461ac of 4 bytes by task 22793 on cpu 1:
send_to_group fs/notify/fsnotify.c:299 [inline]
fsnotify+0x723/0xe70 fs/notify/fsnotify.c:506
__fsnotify_parent+0x2f3/0x430 fs/notify/fsnotify.c:225
fsnotify_parent include/linux/fsnotify.h:68 [inline]
fsnotify_file include/linux/fsnotify.h:90 [inline]
fsnotify_modify include/linux/fsnotify.h:255 [inline]
do_iter_write+0x432/0x4b0 fs/read_write.c:870
vfs_iter_write+0x4c/0x70 fs/read_write.c:907
iter_file_splice_write+0x42a/0x780 fs/splice.c:686
do_splice_from fs/splice.c:764 [inline]
direct_splice_actor+0x80/0xa0 fs/splice.c:933
splice_direct_to_actor+0x345/0x650 fs/splice.c:888
do_splice_direct+0xf5/0x170 fs/splice.c:976
do_sendfile+0x5db/0xca0 fs/read_write.c:1257
__do_sys_sendfile64 fs/read_write.c:1312 [inline]
__se_sys_sendfile64 fs/read_write.c:1304 [inline]
__x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22793 Comm: syz-executor.4 Not tainted 5.10.0-rc6-syzkaller #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.