syzbot

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refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 40 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 UID: 0 PID: 40 Comm: kauditd 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 18 ef 10 fd 84 db 0f 85 66 ff ff ff e8 2b f4 10 fd c6 05 08 80 bf 0b 01 90 48 c7 c7 20 38 f1 8b e8 b7 28 cf fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 08 f4 10 fd 0f b6 1d e3 7f bf 0b 31
RSP: 0018:ffffc900006f8bd8 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817b6ee8
RDX: ffff88801cb30000 RSI: ffffffff817b6ef5 RDI: 0000000000000001
RBP: ffff88803a07c778 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88803a07c778
R13: ffff88804657b000 R14: 0000000000000015 R15: 1ffff11003a7d80c
FS:  0000000000000000(0000) GS:ffff8880d6cd6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd264c61d58 CR3: 000000004cfc5000 CR4: 0000000000352ef0
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:2718 [inline]
 vring_interrupt+0x31e/0x400 drivers/virtio/virtio_ring.c:2693
 __handle_irq_event_percpu+0x236/0x920 kernel/irq/handle.c:203
 handle_irq_event_percpu kernel/irq/handle.c:240 [inline]
 handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:257
 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+0xd0/0x2f0 arch/x86/kernel/irq.c:325
 common_interrupt+0x61/0xe0 arch/x86/kernel/irq.c:318
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
RIP: 0010:handle_softirqs+0x1dd/0x8e0 kernel/softirq.c:608
Code: 88 6c 24 26 4c 89 7c 24 18 48 c7 c7 20 ce 8b 8b e8 b8 29 e9 09 65 66 c7 05 96 2e 27 12 00 00 e8 b9 c8 47 00 fb bb ff ff ff ff <49> c7 c7 c0 c0 00 8e 41 0f bc dc 83 c3 01 0f 85 a4 00 00 00 e9 b1
RSP: 0018:ffffc900006f8f28 EFLAGS: 00000202
RAX: 000000000000a5f8 RBX: 00000000ffffffff RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff8db03f74 RDI: ffffffff8bf1ea40
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff908339d7 R11: 0000000000000001 R12: 0000000000000280
R13: 000000000000000a R14: 1ffff920000df1ed R15: ffffed1003966000
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x109/0x170 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1052
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:console_flush_all+0x9a2/0xc60 kernel/printk/printk.c:3200
Code: 00 e8 d2 4c 29 00 9c 5b 81 e3 00 02 00 00 31 ff 48 89 de e8 80 46 21 00 48 85 db 0f 85 55 01 00 00 e8 02 4b 21 00 fb 4c 89 e0 <48> c1 e8 03 42 80 3c 38 00 0f 84 11 ff ff ff 4c 89 e7 e8 27 d2 89
RSP: 0018:ffffc9000078f9b8 EFLAGS: 00000293
RAX: ffffffff8f073db8 RBX: 0000000000000000 RCX: ffffffff819beda0
RDX: ffff88801cb30000 RSI: ffffffff819bedae RDI: 0000000000000007
RBP: 0000000000000000 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffffffff8f073db8
R13: ffffffff8f073d60 R14: ffffc9000078fa48 R15: dffffc0000000000
 __console_flush_and_unlock kernel/printk/printk.c:3258 [inline]
 console_unlock+0xd8/0x210 kernel/printk/printk.c:3298
 vprintk_emit+0x3d7/0x680 kernel/printk/printk.c:2423
 _printk+0xc7/0x100 kernel/printk/printk.c:2448
 kauditd_printk_skb kernel/audit.c:583 [inline]
 kauditd_hold_skb+0x205/0x250 kernel/audit.c:618
 kauditd_send_queue+0x239/0x290 kernel/audit.c:803
 kauditd_thread+0x623/0xa70 kernel/audit.c:927
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
----------------
Code disassembly (best guess):
   0:	88 6c 24 26          	mov    %ch,0x26(%rsp)
   4:	4c 89 7c 24 18       	mov    %r15,0x18(%rsp)
   9:	48 c7 c7 20 ce 8b 8b 	mov    $0xffffffff8b8bce20,%rdi
  10:	e8 b8 29 e9 09       	call   0x9e929cd
  15:	65 66 c7 05 96 2e 27 	movw   $0x0,%gs:0x12272e96(%rip)        # 0x12272eb5
  1c:	12 00 00
  1f:	e8 b9 c8 47 00       	call   0x47c8dd
  24:	fb                   	sti
  25:	bb ff ff ff ff       	mov    $0xffffffff,%ebx
* 2a:	49 c7 c7 c0 c0 00 8e 	mov    $0xffffffff8e00c0c0,%r15 <-- trapping instruction
  31:	41 0f bc dc          	bsf    %r12d,%ebx
  35:	83 c3 01             	add    $0x1,%ebx
  38:	0f 85 a4 00 00 00    	jne    0xe2
  3e:	e9                   	.byte 0xe9
  3f:	b1                   	.byte 0xb1