[moderation] [exfat?] KCSAN: data-race in has_bh_in_lru / invalidate_bh_lru (9)

[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=10fe2b3a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7cbb341929b72cb5
dashboard link: https://syzkaller.appspot.com/bug?extid=f675e69be7135b609a50
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [hiro...@mail.parknet.co.jp linki...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org sj155...@samsung.com]

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+f675e6...@syzkaller.appspotmail.com

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

write to 0xffff888237d275d0 of 8 bytes by task 21099 on cpu 1:
__invalidate_bh_lrus fs/buffer.c:1530 [inline]
invalidate_bh_lru+0x89/0xe0 fs/buffer.c:1542
csd_do_func kernel/smp.c:136 [inline]
smp_call_function_many_cond+0x865/0xc30 kernel/smp.c:868
on_each_cpu_cond_mask+0x3c/0x80 kernel/smp.c:1043
on_each_cpu_cond include/linux/smp.h:105 [inline]
invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1561
kill_bdev block/bdev.c:90 [inline]
set_blocksize+0x235/0x2c0 block/bdev.c:207
sb_set_blocksize+0x93/0x170 block/bdev.c:240
sb_min_blocksize+0x53/0x60 block/bdev.c:255
fat_fill_super+0x332/0x1ce0 fs/fat/inode.c:1600
vfat_fill_super+0x24/0x30 fs/fat/namei_vfat.c:1196
get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
get_tree_bdev+0x1f/0x30 fs/super.c:1717
vfat_get_tree+0x1c/0x30 fs/fat/namei_vfat.c:1201
vfs_get_tree+0x57/0x1d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3760 [inline]
do_new_mount+0x288/0x8d0 fs/namespace.c:3836
path_mount+0x4d0/0xbc0 fs/namespace.c:4146
do_mount fs/namespace.c:4159 [inline]
__do_sys_mount fs/namespace.c:4348 [inline]
__se_sys_mount+0x28c/0x2e0 fs/namespace.c:4325
__x64_sys_mount+0x67/0x80 fs/namespace.c:4325
x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
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 0xffff888237d275d0 of 8 bytes by task 3308 on cpu 0:
has_bh_in_lru+0x35/0x1f0 fs/buffer.c:1552
smp_call_function_many_cond+0x2a9/0xc30 kernel/smp.c:821
on_each_cpu_cond_mask+0x3c/0x80 kernel/smp.c:1043
on_each_cpu_cond include/linux/smp.h:105 [inline]
invalidate_bh_lrus+0x2a/0x30 fs/buffer.c:1561
kill_bdev block/bdev.c:90 [inline]
blkdev_flush_mapping+0x9a/0x1a0 block/bdev.c:728
blkdev_put_whole block/bdev.c:735 [inline]
bdev_release+0x2bf/0x3d0 block/bdev.c:1160
blkdev_release+0x15/0x20 block/fops.c:706
__fput+0x29b/0x650 fs/file_table.c:469
____fput+0x1c/0x30 fs/file_table.c:497
task_work_run+0x130/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8881079ffc30 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3308 Comm: syz-executor Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
==================================================================


---
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