syzbot

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BUG: KCSAN: data-race in set_nlink / set_nlink

read to 0xffff888106cea780 of 4 bytes by task 3639 on cpu 1:
 set_nlink+0x29/0xb0 fs/inode.c:-1
 kernfs_refresh_inode fs/kernfs/inode.c:180 [inline]
 kernfs_iop_permission+0x1e2/0x220 fs/kernfs/inode.c:288
 do_inode_permission fs/namei.c:526 [inline]
 inode_permission+0x182/0x300 fs/namei.c:593
 may_lookup fs/namei.c:1845 [inline]
 link_path_walk+0x14d/0x8b0 fs/namei.c:2451
 path_openat+0x1de/0x2170 fs/namei.c:4035
 do_filp_open+0x109/0x230 fs/namei.c:4066
 do_sys_openat2+0xa6/0x110 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_openat fs/open.c:1460 [inline]
 __se_sys_openat fs/open.c:1455 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1455
 x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
 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

write to 0xffff888106cea780 of 4 bytes by task 3005 on cpu 0:
 set_nlink+0x99/0xb0 fs/inode.c:458
 kernfs_refresh_inode fs/kernfs/inode.c:180 [inline]
 kernfs_iop_permission+0x1e2/0x220 fs/kernfs/inode.c:288
 do_inode_permission fs/namei.c:526 [inline]
 inode_permission+0x182/0x300 fs/namei.c:593
 may_lookup fs/namei.c:1845 [inline]
 link_path_walk+0x14d/0x8b0 fs/namei.c:2451
 path_lookupat+0x63/0x2a0 fs/namei.c:2659
 filename_lookup+0x147/0x340 fs/namei.c:2689
 vfs_statx+0x9d/0x380 fs/stat.c:350
 vfs_fstatat+0xe1/0x160 fs/stat.c:372
 __do_sys_newfstatat fs/stat.c:536 [inline]
 __se_sys_newfstatat+0x55/0x260 fs/stat.c:530
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:530
 x64_sys_call+0x2c22/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:263
 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: 0x00000009 -> 0x00000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3005 Comm: udevd Not tainted 6.15.0-rc6-syzkaller-00208-g3c21441eeffc #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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