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BUG: KCSAN: data-race in __d_instantiate / path_lookupat

write to 0xffff888107e7b570 of 8 bytes by task 27255 on cpu 0:
 __d_set_inode_and_type fs/dcache.c:407 [inline]
 __d_instantiate+0x1db/0x390 fs/dcache.c:1985
 d_make_persistent+0x78/0x110 fs/dcache.c:2803
 shmem_mknod+0x15f/0x170 mm/shmem.c:3905
 shmem_mkdir+0x33/0x70 mm/shmem.c:3947
 vfs_mkdir+0x294/0x3e0 fs/namei.c:5233
 filename_mkdirat+0x138/0x300 fs/namei.c:5266
 __do_sys_mkdirat fs/namei.c:5287 [inline]
 __se_sys_mkdirat+0x32/0xf0 fs/namei.c:5284
 __x64_sys_mkdirat+0x43/0x50 fs/namei.c:5284
 x64_sys_call+0x2c4e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:259
 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 0xffff888107e7b570 of 8 bytes by task 27257 on cpu 1:
 step_into fs/namei.c:2138 [inline]
 walk_component fs/namei.c:2285 [inline]
 lookup_last fs/namei.c:2780 [inline]
 path_lookupat+0x228/0x500 fs/namei.c:2804
 filename_lookup+0x190/0x390 fs/namei.c:2833
 filename_setxattr+0x56/0x410 fs/xattr.c:659
 path_setxattrat+0x2be/0x310 fs/xattr.c:708
 __do_sys_setxattr fs/xattr.c:742 [inline]
 __se_sys_setxattr fs/xattr.c:738 [inline]
 __x64_sys_setxattr+0x6e/0x90 fs/xattr.c:738
 x64_sys_call+0x2ee2/0x3020 arch/x86/include/generated/asm/syscalls_64.h:189
 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: 0x0000000000000000 -> 0xffff88811d121aa8

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 27257 Comm: syz.0.6689 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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