From: syzbot <syzbot+13eb8132f7693fe21d7d@syzkaller.appspotmail.com>
To: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
magiclinan@didiglobal.com, mingo@redhat.com, song@kernel.org,
syzkaller-bugs@googlegroups.com, tglx@kernel.org,
x86@kernel.org, xiao@kernel.org, yukuai@fnnas.com,
yukuai@fygo.io
Subject: Re: [syzbot] [kernel?] possible deadlock in md_start_sync
Date: Wed, 14 Oct 2026 09:19:32 -0700 [thread overview]
Message-ID: <6acfab94.38256f13.2006af.0129.GAE@google.com> (raw)
In-Reply-To: <6a6e88a1.13bfb6d0.1ecdd5.0261.GAE@google.com>
syzbot has found a reproducer for the following issue on:
HEAD commit: 4056b3c9d3c9 Merge tag 'nios2_update_for_v7.4' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15334e8e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7d1b274ca9837366
dashboard link: https://syzkaller.appspot.com/bug?extid=13eb8132f7693fe21d7d
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=175a6999580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10da6999580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-4056b3c9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/811a43c89106/vmlinux-4056b3c9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2bb4f3abea76/bzImage-4056b3c9.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+13eb8132f7693fe21d7d@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/0:5/5422 is trying to acquire lock:
ffff8880133d8358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: mddev_lock_nointr drivers/md/md.h:734 [inline]
ffff8880133d8358 (&mddev->reconfig_mutex){+.+.}-{4:4}, at: md_start_sync+0x179/0x1010 drivers/md/md.c:10275
but task is already holding lock:
ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}:
process_one_work kernel/workqueue.c:3372 [inline]
process_scheduled_works+0xc03/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #2 ((wq_completion)md_misc){+.+.}-{0:0}:
touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4111
__flush_workqueue+0x148/0x1470 kernel/workqueue.c:4153
md_alloc+0x32/0xf20 drivers/md/md.c:6334
md_alloc_and_put+0x1a/0x1f0 drivers/md/md.c:6423
blk_probe_dev block/genhd.c:888 [inline]
blk_request_module+0x27d/0x2a0 block/genhd.c:-1
blkdev_get_no_open+0x3f/0xe0 block/bdev.c:870
blkdev_open+0x1d7/0x600 block/fops.c:670
do_dentry_open+0x816/0x1380 fs/open.c:996
vfs_open+0x3b/0x340 fs/open.c:1101
do_open fs/namei.c:4866 [inline]
path_openat+0x1443/0x1d60 fs/namei.c:5029
do_file_open+0x23e/0x4a0 fs/namei.c:5058
do_sys_openat2+0x115/0x200 fs/open.c:1417
do_sys_open fs/open.c:1423 [inline]
__do_sys_openat fs/open.c:1439 [inline]
__se_sys_openat fs/open.c:1434 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1434
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (major_names_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
blk_probe_dev block/genhd.c:885 [inline]
blk_request_module+0x35/0x2a0 block/genhd.c:901
blkdev_get_no_open+0x3f/0xe0 block/bdev.c:870
bdev_file_open_by_dev+0xa0/0x240 block/bdev.c:1091
md_import_device+0x2e9/0x650 drivers/md/md.c:3847
md_add_new_disk+0x280/0x1850 drivers/md/md.c:7546
md_ioctl+0x200a/0x2610 drivers/md/md.c:8499
blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798
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+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&mddev->reconfig_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
mddev_lock_nointr drivers/md/md.h:734 [inline]
md_start_sync+0x179/0x1010 drivers/md/md.c:10275
process_one_work kernel/workqueue.c:3396 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
other info that might help us debug this:
Chain exists of:
&mddev->reconfig_mutex --> (wq_completion)md_misc --> (work_completion)(&mddev->sync_work)
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((work_completion)(&mddev->sync_work));
lock((wq_completion)md_misc);
lock((work_completion)(&mddev->sync_work));
lock(&mddev->reconfig_mutex);
*** DEADLOCK ***
locks held by kworker/0:5/5422: 2, last CPU#0:
#0: ffff888031699d40 ((wq_completion)md_misc){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffff888031699d40 ((wq_completion)md_misc){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffff888031699d40 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
#0: ffff888031699d40 ((wq_completion)md_misc){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
#1: ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#1: ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#1: ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
#1: ffffc9000293fc40 ((work_completion)(&mddev->sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
stack backtrace:
CPU: 0 UID: 0 PID: 5422 Comm: kworker/0:5 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
Workqueue: md_misc md_start_sync
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
check_prev_add kernel/locking/lockdep.c:3209 [inline]
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
mddev_lock_nointr drivers/md/md.h:734 [inline]
md_start_sync+0x179/0x1010 drivers/md/md.c:10275
process_one_work kernel/workqueue.c:3396 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
prev parent reply other threads:[~2026-10-14 16:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-02 0:00 [syzbot] [raid?] possible deadlock in md_start_sync syzbot
2026-09-14 21:21 ` [syzbot] [kernel?] " syzbot
2026-10-14 16:19 ` syzbot [this message]
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