syzbot

blk_update_request: I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
Buffer I/O error on dev nbd0, logical block 0, async page read
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refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 150 at lib/refcount.c:28 refcount_warn_saturate+0x11b/0x1a0 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 150 Comm: kworker/1:1H Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: kblockd blk_mq_run_work_fn
RIP: 0010:refcount_warn_saturate+0x11b/0x1a0 lib/refcount.c:28
Code: 09 01 48 c7 c7 a0 6b 59 8a e8 81 b2 c3 05 0f 0b eb c4 e8 18 f5 9c fd c6 05 2d 20 7b 09 01 48 c7 c7 00 6c 59 8a e8 65 b2 c3 05 <0f> 0b eb a8 e8 fc f4 9c fd c6 05 0e 20 7b 09 01 48 c7 c7 40 6b 59
RSP: 0018:ffffc900016cf7e8 EFLAGS: 00010246
RAX: aab5c44c7255df00 RBX: 0000000000000003 RCX: ffff88801bba9dc0
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc900016cf990 R08: dffffc0000000000 R09: ffffed1017224f2c
R10: ffffed1017224f2c R11: 1ffff11017224f2b R12: ffffc900016cfaa0
R13: ffff888020958050 R14: 0000000000000003 R15: 1ffff1100412b009
FS:  0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001e42d000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 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
 </TASK>