syzbot

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BUG: KCSAN: data-race in __dentry_kill / retain_dentry

write to 0xffff888134c7b300 of 4 bytes by task 4897 on cpu 0:
 retain_dentry+0x1c3/0x240 fs/dcache.c:659
 dput+0x10e/0x420 fs/dcache.c:873
 __fput+0x3ab/0x4e0 fs/file_table.c:293
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x16b/0x1a0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888134c7b300 of 4 bytes by task 17427 on cpu 1:
 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:3123 [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: 1 PID: 17427 Comm: systemd-udevd Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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