------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 20 at lib/refcount.c:28 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 20 Comm: ksoftirqd/1 Not tainted 5.15.182-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
lr : refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
sp : ffff80001b377b40
x29: ffff80001b377b40 x28: fffffbffeffd0dc0 x27: 1fffe00019983403
x26: 1fffe00019983403 x25: 0000000000000000 x24: 0000000000000001
x23: dfff800000000000 x22: fffffbffeffd0e88 x21: 0000000000000000
x20: ffff0000ccc1a0e8 x19: ffff80001658e000 x18: 0000000000000101
x17: 0000000000000000 x16: ffff8000111a53fc x15: 0000000000000012
x14: 0000000000000000 x13: 1ffff0000282a06b x12: 0000000000ff0100
x11: 0000000000000100 x10: 0000000000000000 x9 : 62591096a0e7eb00
x8 : 62591096a0e7eb00 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000000 x3 : ffff800008503828

x2 : 0000000000000001 x1 : 0000000100000100 x0 : 0000000000000026
Call trace:
 refcount_warn_saturate+0x154/0x1f8 lib/refcount.c:28
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 blk_mq_free_request+0x434/0x578 block/blk-mq.c:543
 __blk_mq_end_request+0x30c/0x344 block/blk-mq.c:568
 blk_mq_end_request+0x68/0x88 block/blk-mq.c:577
 nbd_complete_rq+0x48/0x160 drivers/block/nbd.c:360
 blk_complete_reqs block/blk-mq.c:587 [inline]
 blk_done_softirq+0x11c/0x168 block/blk-mq.c:592
 handle_softirqs+0x344/0xbf0 kernel/softirq.c:558
 run_ksoftirqd+0x7c/0x2a0 kernel/softirq.c:925
 smpboot_thread_fn+0x4b0/0x920 kernel/smpboot.c:164
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
irq event stamp: 489577
hardirqs last  enabled at (489576): [<ffff8000082f64d8>] console_unlock+0xc6c/0x133c kernel/printk/printk.c:2748
hardirqs last disabled at (489577): [<ffff8000111a0cd0>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:396
softirqs last  enabled at (489548): [<ffff80000819d0d8>] softirq_handle_end kernel/softirq.c:401 [inline]
softirqs last  enabled at (489548): [<ffff80000819d0d8>] handle_softirqs+0xa4c/0xbf0 kernel/softirq.c:586
softirqs last disabled at (489555): [<ffff80000819f98c>] run_ksoftirqd+0x7c/0x2a0 kernel/softirq.c:925
---[ end trace 7922ed304258f676 ]---