[moderation] [mm?] KCSAN: data-race in fill_mg_cmtime / shmem_unlink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 158f238aa69d Merge tag 'for-linus-6.13-rc1-tag' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16cb5ac0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=44f4147e19698730
dashboard link: https://syzkaller.appspot.com/bug?extid=981e2f2af3b7fc150759
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org 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/621d460e9953/disk-158f238a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1449b0450720/vmlinux-158f238a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f1ace1b10c4a/bzImage-158f238a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+981e2f...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fill_mg_cmtime / shmem_unlink

write to 0xffff8881021769a4 of 4 bytes by task 4131 on cpu 1:
inode_set_mtime_to_ts include/linux/fs.h:1648 [inline]
shmem_unlink+0x13b/0x170 mm/shmem.c:3757
vfs_unlink+0x275/0x430 fs/namei.c:4523
do_unlinkat+0x237/0x4d0 fs/namei.c:4587
__do_sys_unlink fs/namei.c:4635 [inline]
__se_sys_unlink fs/namei.c:4633 [inline]
__x64_sys_unlink+0x2e/0x40 fs/namei.c:4633
x64_sys_call+0x2329/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881021769a4 of 4 bytes by task 3491 on cpu 0:
inode_get_mtime_nsec include/linux/fs.h:1634 [inline]
inode_get_mtime include/linux/fs.h:1640 [inline]
fill_mg_cmtime+0x58/0x280 fs/stat.c:55
generic_fillattr+0x241/0x330 fs/stat.c:99
shmem_getattr+0x17b/0x200 mm/shmem.c:1174
vfs_getattr_nosec fs/stat.c:208 [inline]
vfs_getattr fs/stat.c:246 [inline]
vfs_statx_path+0x171/0x2d0 fs/stat.c:283
vfs_statx+0xe1/0x170 fs/stat.c:347
vfs_fstatat fs/stat.c:366 [inline]
__do_sys_newfstatat fs/stat.c:530 [inline]
__se_sys_newfstatat+0xdc/0x300 fs/stat.c:524
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:524
x64_sys_call+0x236d/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1750cb41 -> 0x17639159

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3491 Comm: udevd Not tainted 6.12.0-syzkaller-00971-g158f238aa69d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.