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BUG: KCSAN: data-race in retain_dentry / step_into

write to 0xffff88810d9e0a80 of 4 bytes by task 5782 on cpu 1:
 retain_dentry+0x1c3/0x240 fs/dcache.c:659
 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 0xffff88810d9e0a80 of 4 bytes by task 5785 on cpu 0:
 __d_entry_type include/linux/dcache.h:391 [inline]
 d_is_symlink include/linux/dcache.h:421 [inline]
 step_into+0x158/0xe80 fs/namei.c:1695
 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]
 path_removexattr+0x4d/0x1d0 fs/xattr.c:797
 __do_sys_lremovexattr fs/xattr.c:822 [inline]
 __se_sys_lremovexattr fs/xattr.c:819 [inline]
 __x64_sys_lremovexattr+0x2f/0x40 fs/xattr.c:819
 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: 5785 Comm: syz-executor.2 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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