syzbot

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BUG: KCSAN: data-race in __dentry_kill / fast_dput

write to 0xffff8881071a5cd0 of 8 bytes by task 3006 on cpu 0:
 __d_drop fs/dcache.c:566 [inline]
 __dentry_kill+0x142/0x4b0 fs/dcache.c:658
 dput+0x5e/0xd0 fs/dcache.c:902
 handle_mounts fs/namei.c:1640 [inline]
 step_into+0x5b2/0x820 fs/namei.c:1976
 walk_component+0x162/0x220 fs/namei.c:2144
 lookup_last fs/namei.c:2636 [inline]
 path_lookupat+0xfe/0x2a0 fs/namei.c:2660
 filename_lookup+0x2d7/0x340 fs/namei.c:2691
 do_readlinkat+0x7d/0x320 fs/stat.c:568
 __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+0x2cf3/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881071a5cd0 of 8 bytes by task 3308 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:359 [inline]
 retain_dentry fs/dcache.c:743 [inline]
 fast_dput+0x5f/0x2c0 fs/dcache.c:839
 dput+0x24/0xd0 fs/dcache.c:896
 do_unlinkat+0x299/0x4c0 fs/namei.c:4646
 __do_sys_unlink fs/namei.c:4689 [inline]
 __se_sys_unlink fs/namei.c:4687 [inline]
 __x64_sys_unlink+0x2e/0x40 fs/namei.c:4687
 x64_sys_call+0x22a6/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88823784aa00 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3308 Comm: udevd Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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