syzbot

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BUG: KCSAN: data-race in set_nlink / set_nlink

read to 0xffff888107cd7d28 of 4 bytes by task 3311 on cpu 0:
 set_nlink+0x29/0xb0 fs/inode.c:-1
 kernfs_refresh_inode fs/kernfs/inode.c:182 [inline]
 kernfs_iop_permission+0x1e2/0x220 fs/kernfs/inode.c:290
 do_inode_permission fs/namei.c:526 [inline]
 inode_permission+0x2de/0x3c0 fs/namei.c:596
 lookup_inode_permission_may_exec fs/namei.c:636 [inline]
 may_lookup fs/namei.c:1908 [inline]
 link_path_walk+0x779/0xe30 fs/namei.c:2545
 path_openat+0x1bf/0x23c0 fs/namei.c:4792
 do_filp_open+0x15d/0x280 fs/namei.c:4823
 do_sys_openat2+0xa6/0x150 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1447
 x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888107cd7d28 of 4 bytes by task 3008 on cpu 1:
 set_nlink+0x99/0xb0 fs/inode.c:458
 kernfs_refresh_inode fs/kernfs/inode.c:182 [inline]
 kernfs_iop_permission+0x1e2/0x220 fs/kernfs/inode.c:290
 do_inode_permission fs/namei.c:526 [inline]
 inode_permission+0x2de/0x3c0 fs/namei.c:596
 lookup_inode_permission_may_exec fs/namei.c:636 [inline]
 may_lookup fs/namei.c:1908 [inline]
 link_path_walk+0x779/0xe30 fs/namei.c:2545
 path_lookupat+0x8c/0x500 fs/namei.c:2753
 filename_lookup+0x190/0x390 fs/namei.c:2783
 vfs_statx+0x9d/0x3b0 fs/stat.c:353
 vfs_fstatat+0x115/0x170 fs/stat.c:375
 __do_sys_newfstatat fs/stat.c:542 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:536
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
 x64_sys_call+0x111f/0x3000 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000009 -> 0x00000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3008 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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