[moderation] [mm?] KCSAN: data-race in generic_fillattr / shmem_symlink (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c22e26bd0906 Merge tag 'landlock-7.0-rc1' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10243e5a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7cbb341929b72cb5
dashboard link: https://syzkaller.appspot.com/bug?extid=67197a361277d25df493
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [ak...@linux-foundation.org baoli...@linux.alibaba.com hu...@google.com linux-...@vger.kernel.org linu...@kvack.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0a97430abcaa/disk-c22e26bd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8ec5adec5713/vmlinux-c22e26bd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d7da85ac0b56/bzImage-c22e26bd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+67197a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in generic_fillattr / shmem_symlink

write to 0xffff888103939df0 of 8 bytes by task 3303 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1658 [inline]
shmem_symlink+0x37a/0x3b0 mm/shmem.c:4169
vfs_symlink+0x106/0x220 fs/namei.c:5615
filename_symlinkat+0xe8/0x2b0 fs/namei.c:5640
__do_sys_symlink fs/namei.c:5667 [inline]
__se_sys_symlink+0x42/0x1b0 fs/namei.c:5663
__x64_sys_symlink+0x31/0x40 fs/namei.c:5663
x64_sys_call+0x2465/0x3020 arch/x86/include/generated/asm/syscalls_64.h:89
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 0xffff888103939df0 of 8 bytes by task 3302 on cpu 1:
inode_get_mtime_sec include/linux/fs.h:1640 [inline]
inode_get_mtime include/linux/fs.h:1650 [inline]
generic_fillattr+0x201/0x340 fs/stat.c:102
shmem_getattr+0x181/0x200 mm/shmem.c:1303
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr+0x48/0x60 fs/stat.c:262
vfs_statx_path+0x28/0x140 fs/stat.c:299
vfs_statx+0xc4/0x170 fs/stat.c:356
vfs_fstatat+0x118/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
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: 0x000000007735954a -> 0x0000000077359565

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3302 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================


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