KCSAN: data-race in __dentry_kill / retain_dentry (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3bb61aa6 Merge tag 'arm64-fixes' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=173edb3b500000
kernel config: https://syzkaller.appspot.com/x/.config?x=c949fed53798f819
dashboard link: https://syzkaller.appspot.com/bug?extid=bc914de700c06240153a
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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+bc914d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __dentry_kill / retain_dentry

write to 0xffff8880095a4cc0 of 4 bytes by task 4890 on cpu 1:
d_lru_add fs/dcache.c:400 [inline]
retain_dentry+0x17f/0x240 fs/dcache.c:657
dput+0x10e/0x420 fs/dcache.c:873
__fput+0x395/0x4d0 fs/file_table.c:294
____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 0xffff8880095a4cc0 of 4 bytes by task 20985 on cpu 0:
dentry_unlist fs/dcache.c:544 [inline]
__dentry_kill+0x1e7/0x450 fs/dcache.c:575
dentry_kill fs/dcache.c:692 [inline]
dput+0x203/0x420 fs/dcache.c:878
handle_mounts fs/namei.c:1389 [inline]
step_into+0x43b/0xe80 fs/namei.c:1691
walk_component+0x190/0x350 fs/namei.c:1867
lookup_last fs/namei.c:2310 [inline]
path_lookupat+0x11d/0x550 fs/namei.c:2334
filename_lookup+0xf2/0x380 fs/namei.c:2367
user_path_at_empty+0x3b/0x50 fs/namei.c:2647
user_path_at include/linux/namei.h:59 [inline]
vfs_statx+0x90/0x270 fs/stat.c:185
vfs_fstatat fs/stat.c:207 [inline]
vfs_lstat include/linux/fs.h:3125 [inline]
__do_sys_newlstat fs/stat.c:362 [inline]
__se_sys_newlstat+0x46/0x250 fs/stat.c:356
__x64_sys_newlstat+0x2d/0x40 fs/stat.c:356
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: 0 PID: 20985 Comm: systemd-udevd 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.