WARNING: lock held when returning to user space in blk_throtl_init

Status: moderation: reported on 2026/10/08 23:15
Subsystems: block
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+4b26c40b218e95c3e1e9@syzkaller.appspotmail.com
First crash: 4d07h, last: 4d07h
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ID Workflow Result Correct Bug Created Started Finished Revision
62f86f52 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING: lock held when returning to user space in blk_throtl_init 2026/10/06 01:38 2026/10/06 01:38 2026/10/06 02:51 1995e6c7

Sample crash report:
================================================
WARNING: lock held when returning to user space!
syzkaller #0 Not tainted
------------------------------------------------
syz.2.937/8554 is leaving the kernel with locks still held!
locks held by syz.2.937/8554: 2, last CPU#1:
 #0: ffff888026c05d80 (&q->q_usage_counter(io)#73){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
 #0: ffff888026c05d80 (&q->q_usage_counter(io)#73){++++}-{0:0}, at: blk_throtl_init+0x27b/0x420 block/blk-throttle.c:1332
 #1: ffff888026c05db8 (&q->q_usage_counter(queue)#57){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
 #1: ffff888026c05db8 (&q->q_usage_counter(queue)#57){+.+.}-{0:0}, at: blk_throtl_init+0x27b/0x420 block/blk-throttle.c:1332

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/04 23:10 upstream 6addb4f38557 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING: lock held when returning to user space in blk_throtl_init
* Struck through repros no longer work on HEAD.