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BUG: KCSAN: data-race in fsnotify / fsnotify

read to 0xffff8880b4e66478 of 4 bytes by task 10436 on cpu 1:
 send_to_group fs/notify/fsnotify.c:218 [inline]
 fsnotify+0x4c1/0x7d0 fs/notify/fsnotify.c:368
 __fsnotify_parent+0x1d6/0x230 fs/notify/fsnotify.c:168
 fsnotify_parent include/linux/fsnotify.h:40 [inline]
 fsnotify_path include/linux/fsnotify.h:50 [inline]
 fsnotify_close include/linux/fsnotify.h:290 [inline]
 __fput+0x374/0x520 fs/file_table.c:266
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880b4e66478 of 4 bytes by task 10442 on cpu 0:
 send_to_group fs/notify/fsnotify.c:206 [inline]
 fsnotify+0x41e/0x7d0 fs/notify/fsnotify.c:368
 __fsnotify_parent+0x1d6/0x230 fs/notify/fsnotify.c:168
 fsnotify_parent include/linux/fsnotify.h:40 [inline]
 fsnotify_path include/linux/fsnotify.h:50 [inline]
 fsnotify_modify include/linux/fsnotify.h:256 [inline]
 do_iter_write fs/read_write.c:974 [inline]
 do_iter_write+0x1e7/0x3c0 fs/read_write.c:951
 vfs_iter_write+0x5c/0x80 fs/read_write.c:983
 iter_file_splice_write+0x4c0/0x7f0 fs/splice.c:746
 do_splice_from fs/splice.c:848 [inline]
 direct_splice_actor+0xa0/0xc0 fs/splice.c:1020
 splice_direct_to_actor+0x215/0x510 fs/splice.c:975
 do_splice_direct+0x161/0x1e0 fs/splice.c:1063
 do_sendfile+0x384/0x7f0 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1519 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0xbe/0x140 fs/read_write.c:1511
 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: 10442 Comm: syz-executor.2 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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