[syzbot] [dm?] WARNING in raid_resume

[syzbot] [dm?] WARNING in raid_resume

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8b7179210b22 Add linux-next specific files for 20261104
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=149d5969580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5dad87d6a9d5ee90
dashboard link: https://syzkaller.appspot.com/bug?extid=8b22a0459202f76b4096
compiler:       Debian clang version 22.1.8 (1~deb13u4), 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/24dabb992a55/disk-8b717921.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/efb6c59219d5/vmlinux-8b717921.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ced4d906c236/bzImage-8b717921.xz

AI-generated root cause summary:
In dm-raid, the target expects the underlying MD sync thread recovery state to
remain frozen (MD_RECOVERY_FROZEN) from creation (raid_ctr()) or postsuspend
(raid_postsuspend()) until resume (raid_resume()). When reshaping a RAID10 array
with a dirty region bitmap, raid_preresume() executes rs_start_reshape(), which
calls raid10_start_reshape(). If an error occurs (such as bitmap resize
failure), raid10_start_reshape() branches to its abort label, which
unconditionally executes `mddev->recovery = 0;`, wiping out MD_RECOVERY_FROZEN.
Because raid_preresume() swallows the reshape failure to continue without
change, the subsequent call to raid_resume() encounters RT_FLAG_RS_SUSPENDED
with MD_RECOVERY_FROZEN missing, triggering the assertion
WARN_ON_ONCE(!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)).

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=8b22a0459202f76b4096

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8b22a0459202f76b4096@syzkaller.appspotmail.com

device-mapper: table: 248:14: thin-pool: Error opening metadata block device (-ENOENT)
device-mapper: ioctl: error adding target to table
mdX: bitmap file is out of date, doing full recovery
------------[ cut here ]------------
!test_bit(MD_RECOVERY_FROZEN, &mddev->recovery)
WARNING: drivers/md/dm-raid.c:4139 at raid_resume+0x11fe/0x1290 drivers/md/dm-raid.c:4139, CPU#0: syz.5.1272/11312
Modules linked in:
CPU: 0 UID: 0 PID: 11312 Comm: syz.5.1272 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026
RIP: 0010:raid_resume+0x11fe/0x1290 drivers/md/dm-raid.c:4139
Code: c6 05 0f 85 fc 08 01 48 c7 c7 40 78 3d 8d be 2d 10 00 00 48 c7 c2 e0 b8 3d 8d e8 2d ec d6 f8 e9 b5 fe ff ff e8 13 95 fb f8 90 <0f> 0b 90 e9 63 fe ff ff e8 05 95 fb f8 90 0f 0b 90 e9 c5 fe ff ff
RSP: 0018:ffffc900039e78c0 EFLAGS: 00010283
RAX: ffffffff88cdbd5d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc90010680000 RSI: 0000000000001342 RDI: 0000000000001343
RBP: ffffc900039e7a40 R08: ffff888078c6c2bf R09: 1ffff1100f18d857
R10: dffffc0000000000 R11: ffffed100f18d858 R12: 1ffff9200073cf28
R13: ffff888078c6c058 R14: dffffc0000000000 R15: ffff888078c6c000
FS:  00007fbfa88c06c0(0000) GS:ffff888123161000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005561081d2138 CR3: 000000007ce32000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000001800
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dm_table_resume_targets+0x299/0x3f0 drivers/md/dm-table.c:2204
 __dm_resume+0x22/0x1d0 drivers/md/dm.c:3117
 dm_resume+0x21a/0x2e0 drivers/md/dm.c:3163
 do_resume drivers/md/dm-ioctl.c:1332 [inline]
 dev_suspend+0x6ff/0xaa0 drivers/md/dm-ioctl.c:1368
 ctl_ioctl drivers/md/dm-ioctl.c:2221 [inline]
 dm_ctl_ioctl+0x9ec/0xe10 drivers/md/dm-ioctl.c:2243
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x16a/0x530 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x00007fbfa799fb19
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fbfa88c0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fbfa7c25fa0 RCX: 00007fbfa799fb19
RDX: 0000200000000480 RSI: 00000000c138fd06 RDI: 0000000000000003
RBP: 00007fbfa7a37b70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbfa7c26038 R14: 00007fbfa7c25fa0 R15: 00007fffea1356a8
 </TASK>


---
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[PATCH] md/raid10: preserve recovery flags on reshape abort

[Hristos Nenkov]

raid10_start_reshape() can fail while resizing a bitmap before it
changes any recovery bits on its success path. Its abort path nevertheless
clears the entire mddev->recovery bitmap.

dm-raid keeps MD_RECOVERY_FROZEN set across suspend and resume. If RAID10
reshape setup fails, raid_preresume() logs the failure and continues with
resume. Clearing the bitmap removes MD_RECOVERY_FROZEN and makes
raid_resume() hit its invariant warning.

Do not clear mddev->recovery from the RAID10 abort path. The error paths
reach abort before raid10_start_reshape() modifies the recovery bits, so
there is no personality-owned recovery state to roll back there.

Fixes: bb63a7019df9 ("md/raid10: resize bitmap when required during reshape.")
Reported-by: syzbot+8b22a0459202f76b4096@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8b22a0459202f76b4096
Signed-off-by: Hristos Nenkov <nenkov2004@gmail.com>
---
 drivers/md/raid10.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 066c43154..1fd3f5f4f 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4490,7 +4490,6 @@ static int raid10_start_reshape(struct mddev *mddev)
 	return 0;
 
 abort:
-	mddev->recovery = 0;
 	spin_lock_irq(&conf->device_lock);
 	conf->geo = conf->prev;
 	mddev->raid_disks = conf->geo.raid_disks;

base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9
-- 
2.43.0