[v6.6] kernel BUG in submit_bh_wbc

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d27334b2888c Linux 6.6.151
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10a36149580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0bc3d90c30838b5
dashboard link: https://syzkaller.appspot.com/bug?extid=0e25ce8d777866a3bd1d
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/695139abd971/disk-d27334b2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b11fc121442a/vmlinux-d27334b2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e226f54f9286/bzImage-d27334b2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0e25ce...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/buffer.c:2795!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 6557 Comm: kmmpd-loop0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:submit_bh_wbc+0x566/0x580 fs/buffer.c:2795
Code: e8 af f5 87 ff be 00 10 00 00 48 c7 c7 a0 6f 26 8d 4c 89 ea e8 eb 77 67 02 e9 8b fe ff ff e8 91 f5 87 ff 0f 0b e8 8a f5 87 ff <0f> 0b e8 83 f5 87 ff 0f 0b e8 7c f5 87 ff 0f 0b e8 75 f5 87 ff 0f
RSP: 0018:ffffc90003167cc0 EFLAGS: 00010293
RAX: ffffffff81ff7c96 RBX: 0000000000000000 RCX: ffff88802412da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000003801 R08: ffff88805d19048f R09: 1ffff1100ba32091
R10: dffffc0000000000 R11: ffffed100ba32092 R12: 1ffff1100ba32091
R13: 0000000000000000 R14: ffff88805d190488 R15: ffff88807da9e000
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2da1dff8 CR3: 0000000025758000 CR4: 00000000003506f0
Call Trace:
<TASK>
write_mmp_block_thawed+0x3b1/0x540 fs/ext4/mmp.c:51
write_mmp_block+0x129/0x390 fs/ext4/mmp.c:67
kmmpd+0x344/0x990 fs/ext4/mmp.c:178
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:submit_bh_wbc+0x566/0x580 fs/buffer.c:2795
Code: e8 af f5 87 ff be 00 10 00 00 48 c7 c7 a0 6f 26 8d 4c 89 ea e8 eb 77 67 02 e9 8b fe ff ff e8 91 f5 87 ff 0f 0b e8 8a f5 87 ff <0f> 0b e8 83 f5 87 ff 0f 0b e8 7c f5 87 ff 0f 0b e8 75 f5 87 ff 0f
RSP: 0018:ffffc90003167cc0 EFLAGS: 00010293
RAX: ffffffff81ff7c96 RBX: 0000000000000000 RCX: ffff88802412da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000003801 R08: ffff88805d19048f R09: 1ffff1100ba32091
R10: dffffc0000000000 R11: ffffed100ba32092 R12: 1ffff1100ba32091
R13: 0000000000000000 R14: ffff88805d190488 R15: ffff88807da9e000
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd9981ef2f8 CR3: 0000000025758000 CR4: 00000000003506f0


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