KCSAN: data-race in inode_permission / setattr

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in inode_permission / setattr_copy (2) fs	6				1	10d	10d	0/29	moderation: reported on 2026/01/18 20:27

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BUG: KCSAN: data-race in inode_permission / setattr_copy

write to 0xffff88811e136f00 of 2 bytes by task 12647 on cpu 0:
 setattr_copy+0x199/0x4b0 fs/attr.c:352
 shmem_setattr+0x566/0x840 mm/shmem.c:1338
 notify_change+0x806/0x890 fs/attr.c:552
 chmod_common+0x138/0x270 fs/open.c:650
 do_fchmodat+0xcd/0x180 fs/open.c:697
 __do_sys_fchmodat fs/open.c:716 [inline]
 __se_sys_fchmodat fs/open.c:713 [inline]
 __x64_sys_fchmodat+0x42/0x50 fs/open.c:713
 x64_sys_call+0x2891/0x3000 arch/x86/include/generated/asm/syscalls_64.h:269
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811e136f00 of 2 bytes by task 12646 on cpu 1:
 devcgroup_inode_permission include/linux/device_cgroup.h:21 [inline]
 inode_permission+0x8d/0x310 fs/namei.c:597
 may_lookup fs/namei.c:1858 [inline]
 link_path_walk+0x162/0x900 fs/namei.c:2467
 path_lookupat+0x63/0x2a0 fs/namei.c:2675
 filename_lookup+0x147/0x340 fs/namei.c:2705
 user_path_at+0x3e/0x130 fs/namei.c:3215
 do_fchmodat+0x9c/0x180 fs/open.c:695
 __do_sys_fchmodat fs/open.c:716 [inline]
 __se_sys_fchmodat fs/open.c:713 [inline]
 __x64_sys_fchmodat+0x42/0x50 fs/open.c:713
 x64_sys_call+0x2891/0x3000 arch/x86/include/generated/asm/syscalls_64.h:269
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x41c0 -> 0x4ffb

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12646 Comm: syz.6.3065 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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