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BUG: KCSAN: data-race in setattr_copy / vfs_write

write to 0xffff88810950c938 of 2 bytes by task 16962 on cpu 0:
 setattr_copy+0x199/0x4a0 fs/attr.c:344
 shmem_setattr+0x566/0x840 mm/shmem.c:1338
 notify_change+0x872/0x8f0 fs/attr.c:546
 chmod_common+0x138/0x270 fs/open.c:650
 do_fchmodat+0xcd/0x180 fs/open.c:697
 __do_sys_chmod fs/open.c:721 [inline]
 __se_sys_chmod fs/open.c:719 [inline]
 __x64_sys_chmod+0x38/0x50 fs/open.c:719
 x64_sys_call+0x2920/0x3000 arch/x86/include/generated/asm/syscalls_64.h:91
 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 0xffff88810950c938 of 2 bytes by task 16955 on cpu 1:
 file_end_write include/linux/fs.h:3129 [inline]
 vfs_write+0x757/0x960 fs/read_write.c:694
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 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: 0x8000 -> 0x8120

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16955 Comm: syz.5.5054 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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