syzbot

Buffer I/O error on dev nbd4, logical block 0, async page read
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refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 4739 at lib/refcount.c:28 refcount_warn_saturate+0x14e/0x1a0 lib/refcount.c:28
Modules linked in:

CPU: 0 PID: 4739 Comm: kworker/0:2H Not tainted 5.15.178-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: kblockd blk_mq_run_work_fn

RIP: 0010:refcount_warn_saturate+0x14e/0x1a0 lib/refcount.c:28
Code: 09 01 48 c7 c7 c0 b5 f9 8a e8 2e 42 38 fd 0f 0b eb 8d e8 85 a8 6c fd c6 05 cb 10 e3 09 01 48 c7 c7 20 b6 f9 8a e8 12 42 38 fd <0f> 0b e9 6e ff ff ff e8 66 a8 6c fd c6 05 ad 10 e3 09 01 48 c7 c7
RSP: 0018:ffffc90003f7f788 EFLAGS: 00010246

RAX: 0c35e3aff4926b00 RBX: 0000000000000003 RCX: ffff888078993b80
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff8166aa8c R09: ffffed10171c4f24
R10: 0000000000000000 R11: dffffc0000000001 R12: ffff88802120a000
R13: dffffc0000000000 R14: ffffc90003f7fa20 R15: ffff88802136fc00
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbcd60abd58 CR3: 000000007443e000 CR4: 00000000003506f0
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+0xc47/0x1f30 block/blk-mq.c:1408
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:200 [inline]
 blk_mq_do_dispatch_sched+0x755/0xd50 block/blk-mq-sched.c:214
 __blk_mq_sched_dispatch_requests+0x39b/0x490
 blk_mq_sched_dispatch_requests+0xf3/0x1b0 block/blk-mq-sched.c:366
 __blk_mq_run_hw_queue+0x11a/0x1b0 block/blk-mq.c:1511
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>