[moderation] [fs?] KCSAN: data-race in inode_permission / setattr_copy (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e84d960149e7 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10bda852580000
kernel config: https://syzkaller.appspot.com/x/.config?x=676c6f0212d0c041
dashboard link: https://syzkaller.appspot.com/bug?extid=25e5c6c2070964055082
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e2c3723b9ab1/disk-e84d9601.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5790bc964aa6/vmlinux-e84d9601.xz
kernel image: https://storage.googleapis.com/syzbot-assets/023ce82e3277/bzImage-e84d9601.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+25e5c6...@syzkaller.appspotmail.com

==================================================================
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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