syzbot

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BUG: KCSAN: data-race in lookup_fast / shrink_dentry_list

read-write to 0xffff888187eb4f00 of 4 bytes by task 23855 on cpu 1:
 d_shrink_del fs/dcache.c:516 [inline]
 shrink_dentry_list+0x22d/0x3c0 fs/dcache.c:1166
 shrink_dcache_sb+0x15d/0x290 fs/dcache.c:1295
 reconfigure_super+0x142/0x590 fs/super.c:1058
 do_remount fs/namespace.c:3388 [inline]
 path_mount+0xaf7/0xbc0 fs/namespace.c:4138
 do_mount fs/namespace.c:4159 [inline]
 __do_sys_mount fs/namespace.c:4348 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4325
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4325
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888187eb4f00 of 4 bytes by task 23415 on cpu 0:
 d_revalidate fs/namei.c:1029 [inline]
 lookup_fast+0x72/0x320 fs/namei.c:1877
 walk_component fs/namei.c:2275 [inline]
 link_path_walk+0x51c/0xe30 fs/namei.c:2647
 path_lookupat+0x8c/0x500 fs/namei.c:2803
 filename_lookup+0x190/0x390 fs/namei.c:2833
 user_path_at+0x3e/0x100 fs/namei.c:3612
 ksys_umount fs/namespace.c:2052 [inline]
 __do_sys_umount fs/namespace.c:2060 [inline]
 __se_sys_umount fs/namespace.c:2058 [inline]
 __x64_sys_umount+0x85/0xe0 fs/namespace.c:2058
 x64_sys_call+0x103b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:167
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00140444 -> 0x00100044

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 23415 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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