------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 15996 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 UID: 0 PID: 15996 Comm: syz.5.2849 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 28 9f d7 fc 84 db 0f 85 66 ff ff ff e8 3b a4 d7 fc c6 05 8a d7 af 0b 01 90 48 c7 c7 00 a2 15 8c e8 97 48 96 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 18 a4 d7 fc 0f b6 1d 65 d7 af 0b 31
RSP: 0018:ffffc900006f8d88 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817a4388
RDX: ffff88804a792440 RSI: ffffffff817a4395 RDI: 0000000000000001
RBP: ffff88802a90c998 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88802a90c998
R13: ffff888030b83c00 R14: 0000000000000015 R15: 1ffff110202e300c
FS:  000055556f24d500(0000) GS:ffff8880d69b2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33523ffc CR3: 0000000049380000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000e58e DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 p9_req_put+0x1ec/0x250 net/9p/client.c:404
 req_done+0x1dc/0x2e0 net/9p/trans_virtio.c:147
 vring_interrupt drivers/virtio/virtio_ring.c:2719 [inline]
 vring_interrupt+0x31b/0x400 drivers/virtio/virtio_ring.c:2694
 __handle_irq_event_percpu+0x22c/0x7d0 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:210
 handle_edge_irq+0x3ca/0x9e0 kernel/irq/chip.c:855
 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
 handle_irq arch/x86/kernel/irq.c:254 [inline]
 call_irq_handler arch/x86/kernel/irq.c:310 [inline]
 __common_interrupt+0xcd/0x2f0 arch/x86/kernel/irq.c:325
 common_interrupt+0xba/0xe0 arch/x86/kernel/irq.c:318
 </IRQ>
 <TASK>
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 06 5f 00 f6 48 89 df e8 ee b2 00 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 c5 af f0 f5 65 8b 05 9e 6c 3f 08 85 c0 74 16 5b
RSP: 0018:ffffc90004d57b88 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffff888051e35290 RCX: ffffffff81c3835f
RDX: 0000000000000000 RSI: ffffffff8de52d11 RDI: ffffffff8c163300
RBP: 0000000000000202 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90ab7497 R11: 0000000000000000 R12: ffff888051e35290
R13: ffff888051e34894 R14: ffff888051e34880 R15: ffff888051e3528f
 class_raw_spinlock_irqsave_destructor include/linux/spinlock.h:557 [inline]
 try_to_wake_up+0xa5d/0x1870 kernel/sched/core.c:4216
 wake_up_process kernel/sched/core.c:4459 [inline]
 wake_up_q+0xa1/0x130 kernel/sched/core.c:1084
 futex_wake+0x460/0x530 kernel/futex/waitwake.c:198
 do_futex+0x1e3/0x350 kernel/futex/syscalls.c:107
 __do_sys_futex kernel/futex/syscalls.c:179 [inline]
 __se_sys_futex kernel/futex/syscalls.c:160 [inline]
 __x64_sys_futex+0x1e0/0x4c0 kernel/futex/syscalls.c:160
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbaa9d8ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe77ec9df8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007fbaa9fd5fa8 RCX: 00007fbaa9d8ec29
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fbaa9fd5fa8
RBP: 0000000000000000 R08: 0000000000000021 R09: 0000000277eca0ef
R10: 00007fbaa9fd5fa0 R11: 0000000000000246 R12: 00007fbaa9fd5fac
R13: 00007fbaa9fd5fa0 R14: 0000000000001097 R15: 0000000000000005
 </TASK>
----------------
Code disassembly (best guess):
   0:	f5                   	cmc
   1:	53                   	push   %rbx
   2:	48 8b 74 24 10       	mov    0x10(%rsp),%rsi
   7:	48 89 fb             	mov    %rdi,%rbx
   a:	48 83 c7 18          	add    $0x18,%rdi
   e:	e8 06 5f 00 f6       	call   0xf6005f19
  13:	48 89 df             	mov    %rbx,%rdi
  16:	e8 ee b2 00 f6       	call   0xf600b309
  1b:	f7 c5 00 02 00 00    	test   $0x200,%ebp
  21:	75 23                	jne    0x46
  23:	9c                   	pushf
  24:	58                   	pop    %rax
  25:	f6 c4 02             	test   $0x2,%ah
  28:	75 37                	jne    0x61
* 2a:	bf 01 00 00 00       	mov    $0x1,%edi <-- trapping instruction
  2f:	e8 c5 af f0 f5       	call   0xf5f0aff9
  34:	65 8b 05 9e 6c 3f 08 	mov    %gs:0x83f6c9e(%rip),%eax        # 0x83f6cd9
  3b:	85 c0                	test   %eax,%eax
  3d:	74 16                	je     0x55
  3f:	5b                   	pop    %rbx