[syzbot] [raid?] kernel BUG in raid5_run

[syzbot <syzbot+1f5a7de91d547763f4c8@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    654ae5d73c05 Merge tag 'drm-fixes-2026-09-05' of https://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1305d4f9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=85bc5cc2fc7394d9
dashboard link: https://syzkaller.appspot.com/bug?extid=1f5a7de91d547763f4c8
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-654ae5d7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/79c29503032d/vmlinux-654ae5d7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a650a484f62c/bzImage-654ae5d7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f5a7de91d547763f4c8@syzkaller.appspotmail.com

md/raid
md/raid:md0: not clean -- starting background reconstruction
------------[ cut here ]------------
kernel BUG at drivers/md/raid5.c:8117!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 2 UID: 0 PID: 25223 Comm: syz.2.6302 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:raid5_run+0x11a7/0x1670 drivers/md/raid5.c:8117
Code: 03 00 00 41 8b ae d0 01 00 00 31 ff 89 ee e8 30 51 84 f9 48 c7 44 24 10 00 00 00 00 85 ed 0f 84 44 f4 ff ff e8 aa 56 84 f9 90 <0f> 0b e8 a2 56 84 f9 49 8d 86 e0 00 00 00 48 89 c2 48 89 44 24 60
RSP: 0000:ffffc90025aef9d8 EFLAGS: 00010287
RAX: 00000000000008eb RBX: 0000000000000000 RCX: ffffc90007a8a000
RDX: 0000000000080000 RSI: ffffffff8886e586 RDI: ffff8880722aa580
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000008
R13: 0000000000000000 R14: ffff88804c9e4000 R15: ffff88804c9e4028
FS:  0000000000000000(0000) GS:ffff888096b63000(0063) knlGS:00000000f5456b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000005658921c CR3: 000000004ff23000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 md_run+0xc2f/0x2510 drivers/md/md.c:6779
 do_md_run+0x36/0x660 drivers/md/md.c:6880
 array_state_store+0x9c5/0xcf0 drivers/md/md.c:4765
 md_attr_store+0x1c5/0x330 drivers/md/md.c:6158
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
 __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f97fec
Code: Unable to access opcode bytes at 0xf7f97fc2.
RSP: 002b:00000000f545650c EFLAGS: 00000292 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 000000000000000a RCX: 00000000800007c0
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:raid5_run+0x11a7/0x1670 drivers/md/raid5.c:8117
Code: 03 00 00 41 8b ae d0 01 00 00 31 ff 89 ee e8 30 51 84 f9 48 c7 44 24 10 00 00 00 00 85 ed 0f 84 44 f4 ff ff e8 aa 56 84 f9 90 <0f> 0b e8 a2 56 84 f9 49 8d 86 e0 00 00 00 48 89 c2 48 89 44 24 60
RSP: 0000:ffffc90025aef9d8 EFLAGS: 00010287
RAX: 00000000000008eb RBX: 0000000000000000 RCX: ffffc90007a8a000
RDX: 0000000000080000 RSI: ffffffff8886e586 RDI: ffff8880722aa580
RBP: 0000000000000002 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000008
R13: 0000000000000000 R14: ffff88804c9e4000 R15: ffff88804c9e4028
FS:  0000000000000000(0000) GS:ffff888096b63000(0063) knlGS:00000000f5456b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f7f76ec0 CR3: 000000004ff23000 CR4: 0000000000352ef0


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