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BUG: KCSAN: data-race in __dentry_kill / fast_dput

write to 0xffff8881064f9d90 of 8 bytes by task 12688 on cpu 0:
 __d_drop fs/dcache.c:549 [inline]
 __dentry_kill+0x13e/0x4c0 fs/dcache.c:641
 dput+0x5c/0xd0 fs/dcache.c:885
 handle_mounts fs/namei.c:1639 [inline]
 step_into+0x218/0x820 fs/namei.c:1952
 walk_component+0x169/0x230 fs/namei.c:2120
 lookup_last fs/namei.c:2612 [inline]
 path_lookupat+0x10a/0x2b0 fs/namei.c:2636
 filename_lookup+0x150/0x340 fs/namei.c:2665
 user_path_at+0x3c/0x120 fs/namei.c:3072
 do_mount fs/namespace.c:3897 [inline]
 __do_sys_mount fs/namespace.c:4111 [inline]
 __se_sys_mount+0x24b/0x2d0 fs/namespace.c:4088
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4088
 x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881064f9d90 of 8 bytes by task 12689 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:366 [inline]
 retain_dentry fs/dcache.c:726 [inline]
 fast_dput+0x65/0x2c0 fs/dcache.c:822
 dput+0x24/0xd0 fs/dcache.c:879
 handle_mounts fs/namei.c:1639 [inline]
 step_into+0x218/0x820 fs/namei.c:1952
 walk_component+0x169/0x230 fs/namei.c:2120
 lookup_last fs/namei.c:2612 [inline]
 path_lookupat+0x10a/0x2b0 fs/namei.c:2636
 filename_lookup+0x150/0x340 fs/namei.c:2665
 user_path_at+0x3c/0x120 fs/namei.c:3072
 __do_sys_chdir fs/open.c:557 [inline]
 __se_sys_chdir+0x4c/0x140 fs/open.c:551
 __x64_sys_chdir+0x1f/0x30 fs/open.c:551
 x64_sys_call+0x25cc/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:81
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888237934a08 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12689 Comm: syz.1.3292 Not tainted 6.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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