syzbot

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BUG: KCSAN: data-race in dentry_kill / fast_dput

write to 0xffff8881004b3190 of 8 bytes by task 2979 on cpu 0:
 __d_drop fs/dcache.c:578 [inline]
 dentry_kill+0x139/0x500 fs/dcache.c:824
 finish_dput+0x16/0x1d0 fs/dcache.c:1001
 dput+0x48/0x50 fs/dcache.c:1042
 handle_mounts fs/namei.c:1753 [inline]
 step_into_slowpath+0x38c/0x4c0 fs/namei.c:2104
 step_into fs/namei.c:2152 [inline]
 walk_component fs/namei.c:2288 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x2eb/0x4c0 fs/namei.c:2813
 filename_lookup+0x329/0x390 fs/namei.c:2844
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881004b3190 of 8 bytes by task 3288 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:396 [inline]
 retain_dentry fs/dcache.c:872 [inline]
 fast_dput+0x64/0x2e0 fs/dcache.c:971
 dput+0x1f/0x50 fs/dcache.c:1040
 end_dirop fs/namei.c:2956 [inline]
 filename_unlinkat+0x217/0x410 fs/namei.c:5584
 __do_sys_unlink fs/namei.c:5616 [inline]
 __se_sys_unlink+0x2b/0xe0 fs/namei.c:5613
 __x64_sys_unlink+0x1f/0x30 fs/namei.c:5613
 x64_sys_call+0x2eb6/0x3020 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888237610170 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3288 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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