[moderation] [ext4?] KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8c6bc74c7f89 Merge tag 'v6.16-rc1-smb3-client-fixes' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=166fbd70580000
kernel config: https://syzkaller.appspot.com/x/.config?x=75ba7d6bc4eb7c9d
dashboard link: https://syzkaller.appspot.com/bug?extid=205e7e59a6508d6d688d
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
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/8bb8ff23b86b/disk-8c6bc74c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b8ce1c10350a/vmlinux-8c6bc74c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/eff1a0604096/bzImage-8c6bc74c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+205e7e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru

write to 0xffff888237c26f10 of 8 bytes by task 11183 on cpu 0:
__invalidate_bh_lrus fs/buffer.c:1535 [inline]
invalidate_bh_lru+0x8f/0xf0 fs/buffer.c:1547
csd_do_func kernel/smp.c:134 [inline]
smp_call_function_many_cond+0x237/0xbf0 kernel/smp.c:876
on_each_cpu_cond_mask+0x3c/0x80 kernel/smp.c:1052
on_each_cpu_cond include/linux/smp.h:105 [inline]
invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1566
invalidate_bdev+0x42/0x70 block/bdev.c:100
ext4_put_super+0x624/0x7d0 fs/ext4/super.c:1339
generic_shutdown_super+0xe6/0x210 fs/super.c:643
kill_block_super+0x2a/0x70 fs/super.c:1753
ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7391
deactivate_locked_super+0x72/0x1c0 fs/super.c:474
deactivate_super+0x97/0xa0 fs/super.c:507
cleanup_mnt+0x269/0x2e0 fs/namespace.c:1417
__cleanup_mnt+0x19/0x20 fs/namespace.c:1424
task_work_run+0x12e/0x1a0 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:114
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237c26f10 of 8 bytes by task 11401 on cpu 1:
has_bh_in_lru+0x35/0x1f0 fs/buffer.c:1557
smp_call_function_many_cond+0x389/0xbf0 kernel/smp.c:838
on_each_cpu_cond_mask+0x3c/0x80 kernel/smp.c:1052
on_each_cpu_cond include/linux/smp.h:105 [inline]
invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1566
kill_bdev block/bdev.c:90 [inline]
blkdev_flush_mapping+0x9a/0x1a0 block/bdev.c:712
blkdev_put_whole block/bdev.c:719 [inline]
bdev_release+0x2bf/0x3d0 block/bdev.c:1144
blkdev_release+0x15/0x20 block/fops.c:684
__fput+0x298/0x650 fs/file_table.c:465
____fput+0x1c/0x30 fs/file_table.c:493
task_work_run+0x12e/0x1a0 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:114
exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88811a0ca3a8 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 11401 Comm: syz-executor Not tainted 6.16.0-rc1-syzkaller-00236-g8c6bc74c7f89 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


---
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.