syzbot

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refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 0 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 UID: 0 PID: 0 Comm: swapper/3 Not tainted 6.14.0-rc7-syzkaller-00179-gb3ee1e460951 #0
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 78 19 f5 fc 84 db 0f 85 66 ff ff ff e8 cb 1e f5 fc c6 05 e7 26 86 0b 01 90 48 c7 c7 20 17 d3 8b e8 f7 4c b5 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 a8 1e f5 fc 0f b6 1d c2 26 86 0b 31
RSP: 0018:ffffc90000718be8 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817a2269
RDX: ffff88801dad4880 RSI: ffffffff817a2276 RDI: 0000000000000001
RBP: ffff888024e32228 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888024e32228
R13: ffff88804d1c0400 R14: 0000000000000014 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555f62e808 CR3: 00000000358e8000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:275 [inline]
 __refcount_dec_and_test include/linux/refcount.h:307 [inline]
 refcount_dec_and_test include/linux/refcount.h:325 [inline]
 p9_req_put+0x1ec/0x250 net/9p/client.c:404
 req_done+0x1e7/0x2f0 net/9p/trans_virtio.c:147
 vring_interrupt drivers/virtio/virtio_ring.c:2715 [inline]
 vring_interrupt+0x31b/0x400 drivers/virtio/virtio_ring.c:2690
 __handle_irq_event_percpu+0x229/0x7d0 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+0x263/0xd10 kernel/irq/chip.c:831
 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
 handle_irq arch/x86/kernel/irq.c:249 [inline]
 call_irq_handler arch/x86/kernel/irq.c:261 [inline]
 __common_interrupt+0xdf/0x250 arch/x86/kernel/irq.c:287
 common_interrupt+0x61/0xe0 arch/x86/kernel/irq.c:280
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
RIP: 0010:handle_softirqs+0x1da/0x8f0 kernel/softirq.c:547
Code: 89 44 24 18 48 89 6c 24 10 48 c7 c7 c0 83 6b 8b e8 6b 7d db 09 65 66 c7 05 b9 b9 87 7e 00 00 e8 2c 8b 45 00 fb bb ff ff ff ff <49> c7 c6 c0 b0 e0 8d 41 0f bc dc 83 c3 01 0f 85 a4 00 00 00 e9 b1
RSP: 0018:ffffc90000718f28 EFLAGS: 00000206
RAX: 0000000000045a72 RBX: 00000000ffffffff RCX: 1ffffffff20c4511
RDX: 0000000000000000 RSI: ffffffff8b6cfc80 RDI: ffffffff8bd36a20
RBP: ffff88801dad4880 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90626c17 R11: 0000000000000000 R12: 0000000000000082
R13: 000000000000000a R14: 0000000000000001 R15: 0000000000000000
 __do_softirq kernel/softirq.c:595 [inline]
 invoke_softirq kernel/softirq.c:435 [inline]
 __irq_exit_rcu+0x109/0x170 kernel/softirq.c:662
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:678
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:37 [inline]
RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:92 [inline]
RIP: 0010:default_idle+0xf/0x20 arch/x86/kernel/process.c:744
Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 53 00 0f 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc900001b7e08 EFLAGS: 00000202
RAX: 0000000000045a6d RBX: 0000000000000003 RCX: ffffffff8b579469
RDX: 0000000000000000 RSI: ffffffff8b6cfc80 RDI: ffffffff8bd36a20
RBP: ffffed1003b5a910 R08: 0000000000000001 R09: ffffed100d526f85
R10: ffff88806a937c2b R11: 0000000000000000 R12: 0000000000000003
R13: ffff88801dad4880 R14: ffffffff90626c10 R15: 0000000000000000
 default_idle_call+0x6d/0xb0 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x329/0x3f0 kernel/sched/idle.c:325
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:423
 start_secondary+0x222/0x2b0 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x148
 </TASK>
----------------
Code disassembly (best guess):
   0:	89 44 24 18          	mov    %eax,0x18(%rsp)
   4:	48 89 6c 24 10       	mov    %rbp,0x10(%rsp)
   9:	48 c7 c7 c0 83 6b 8b 	mov    $0xffffffff8b6b83c0,%rdi
  10:	e8 6b 7d db 09       	call   0x9db7d80
  15:	65 66 c7 05 b9 b9 87 	movw   $0x0,%gs:0x7e87b9b9(%rip)        # 0x7e87b9d8
  1c:	7e 00 00
  1f:	e8 2c 8b 45 00       	call   0x458b50
  24:	fb                   	sti
  25:	bb ff ff ff ff       	mov    $0xffffffff,%ebx
* 2a:	49 c7 c6 c0 b0 e0 8d 	mov    $0xffffffff8de0b0c0,%r14 <-- 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