[moderation] [mm?] KCSAN: data-race in generic_fillattr / shmem_symlink (7)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a142da0b2d32 Merge tag 'block-7.2-20260625' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10678a76580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=a46c99c93206dd90baf9
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
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/55c821bde946/disk-a142da0b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/778808d12d2a/vmlinux-a142da0b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ab191ae8905/bzImage-a142da0b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a46c99...@syzkaller.appspotmail.com

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

write to 0xffff8881047393fc of 4 bytes by task 3288 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1655 [inline]
shmem_symlink+0x369/0x3a0 mm/shmem.c:4066
vfs_symlink+0xfd/0x220 fs/namei.c:5656
filename_symlinkat+0xe8/0x2b0 fs/namei.c:5681
__do_sys_symlink fs/namei.c:5708 [inline]
__se_sys_symlink+0x42/0x1b0 fs/namei.c:5704
__x64_sys_symlink+0x31/0x40 fs/namei.c:5704
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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881047393fc of 4 bytes by task 3280 on cpu 1:
inode_get_mtime_nsec include/linux/fs.h:1641 [inline]
inode_get_mtime include/linux/fs.h:1647 [inline]
generic_fillattr+0x214/0x340 fs/stat.c:102
shmem_getattr+0x181/0x200 mm/shmem.c:1302
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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0d7320d7 -> 0x0d7e64da

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3280 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


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