[moderation] [ext4?] KCSAN: data-race in _copy_to_iter / kmmpd

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 872cf28b8df9 Merge tag 'platform-drivers-x86-v6.11-4' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10fc2a29980000
kernel config: https://syzkaller.appspot.com/x/.config?x=3aa0f597417bf8c7
dashboard link: https://syzkaller.appspot.com/bug?extid=c1161218be8dcd8946b9
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fbbe6ab4b479/disk-872cf28b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0dea9f8e7744/vmlinux-872cf28b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c5819bbb608/bzImage-872cf28b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c11612...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in _copy_to_iter / kmmpd

write to 0xffff88814f57c008 of 8 bytes by task 4132 on cpu 0:
kmmpd+0xb8/0x610 fs/ext4/mmp.c:153
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff88814f57c000 of 512 bytes by task 3503 on cpu 1:
instrument_copy_to_user include/linux/instrumented.h:113 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_ubuf include/linux/iov_iter.h:29 [inline]
iterate_and_advance2 include/linux/iov_iter.h:245 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0x126/0xb00 lib/iov_iter.c:185
copy_page_to_iter+0x171/0x2b0 lib/iov_iter.c:362
copy_folio_to_iter include/linux/uio.h:180 [inline]
filemap_read+0x42c/0x690 mm/filemap.c:2676
blkdev_read_iter+0x217/0x2c0 block/fops.c:764
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x5e9/0x6e0 fs/read_write.c:476
ksys_read+0xeb/0x1b0 fs/read_write.c:619
__do_sys_read fs/read_write.c:629 [inline]
__se_sys_read fs/read_write.c:627 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:627
x64_sys_call+0x27d3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:1
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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3503 Comm: udevd Not tainted 6.11.0-rc4-syzkaller-00033-g872cf28b8df9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

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