Buffer I/O error on dev nbd0, logical block 0, async page read ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 1201 at lib/refcount.c:28 refcount_warn_saturate+0x11b/0x1a0 lib/refcount.c:28 Modules linked in: CPU: 0 PID: 1201 Comm: kworker/0:1H Not tainted 5.15.189-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Workqueue: kblockd blk_mq_run_work_fn RIP: 0010:refcount_warn_saturate+0x11b/0x1a0 lib/refcount.c:28 Code: 09 01 48 c7 c7 60 56 59 8a e8 c1 f1 c2 05 0f 0b eb c4 e8 e8 4d 9d fd c6 05 47 54 7b 09 01 48 c7 c7 c0 56 59 8a e8 a5 f1 c2 05 <0f> 0b eb a8 e8 cc 4d 9d fd c6 05 28 54 7b 09 01 48 c7 c7 00 56 59 RSP: 0018:ffffc9000528f7e8 EFLAGS: 00010246 RAX: e7942e32c1a18a00 RBX: 0000000000000003 RCX: ffff8880226c9dc0 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: ffffc9000528f990 R08: dffffc0000000000 R09: fffff52000a51e61 R10: fffff52000a51e61 R11: 1ffff92000a51e60 R12: ffffc9000528faa0 R13: ffff888021088250 R14: 0000000000000003 R15: 1ffff11004211049 FS: 0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055e806d6f950 CR3: 0000000025416000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: blk_mq_end_request block/blk-mq.c:577 [inline] blk_mq_dispatch_rq_list+0xb8b/0x1dd0 block/blk-mq.c:1408 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:200 [inline] blk_mq_do_dispatch_sched+0xabc/0xc40 block/blk-mq-sched.c:214 __blk_mq_sched_dispatch_requests+0x311/0x3f0 block/blk-mq-sched.c:-1 blk_mq_sched_dispatch_requests+0xf4/0x1b0 block/blk-mq-sched.c:366 __blk_mq_run_hw_queue+0xbb/0xf0 block/blk-mq.c:1511 process_one_work+0x863/0x1000 kernel/workqueue.c:2310 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287