syzbot

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BUG: KCSAN: data-race in inode_permission / setattr_copy

write to 0xffff88812476c938 of 2 bytes by task 6264 on cpu 1:
 setattr_copy+0x199/0x4a0 fs/attr.c:344
 shmem_setattr+0x5be/0x7c0 mm/shmem.c:1357
 notify_change+0x872/0x8f0 fs/attr.c:546
 chmod_common+0x141/0x270 fs/open.c:647
 do_fchmodat+0xa4/0x150 fs/open.c:694
 __do_sys_fchmodat fs/open.c:713 [inline]
 __se_sys_fchmodat fs/open.c:710 [inline]
 __x64_sys_fchmodat+0x42/0x50 fs/open.c:710
 x64_sys_call+0x2e6c/0x3000 arch/x86/include/generated/asm/syscalls_64.h:269
 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

read to 0xffff88812476c938 of 2 bytes by task 6265 on cpu 0:
 devcgroup_inode_permission include/linux/device_cgroup.h:21 [inline]
 inode_permission+0x195/0x3c0 fs/namei.c:600
 lookup_inode_permission_may_exec fs/namei.c:639 [inline]
 may_lookup fs/namei.c:1908 [inline]
 link_path_walk+0x899/0xe30 fs/namei.c:2545
 path_lookupat+0x8c/0x500 fs/namei.c:2753
 filename_lookup+0x190/0x390 fs/namei.c:2783
 user_path_at+0x3e/0x130 fs/namei.c:3576
 do_fchmodat+0x77/0x150 fs/open.c:692
 __do_sys_fchmodat fs/open.c:713 [inline]
 __se_sys_fchmodat fs/open.c:710 [inline]
 __x64_sys_fchmodat+0x42/0x50 fs/open.c:710
 x64_sys_call+0x2e6c/0x3000 arch/x86/include/generated/asm/syscalls_64.h:269
 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: 0x41c0 -> 0x4e11

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6265 Comm: syz.4.464 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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