Re: [syzbot] [kvm-x86?] WARNING in hv_tlb_flush_enqueue

[Sean Christopherson <seanjc@google.com>]

On Mon, Jun 22, 2026, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8cd8cf7a07e5 Merge tag 'scsi-misc' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1012a7a1580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e69294ccc24d9da
> dashboard link: https://syzkaller.appspot.com/bug?extid=5d2b94b77112148d1744
> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14c0db7a580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13dd001c580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-8cd8cf7a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b15ef084e059/vmlinux-8cd8cf7a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a22f25c3f8ee/bzImage-8cd8cf7a.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5d2b94b77112148d1744@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> pvqspinlock: lock 0xffff88802c0c8790 has corrupted value 0x0!
> WARNING: kernel/locking/qspinlock_paravirt.h:504 at __pv_queued_spin_unlock_slowpath+0x220/0x2e0 kernel/locking/qspinlock_paravirt.h:504, CPU#0: syz.0.3154/18851
> Modules linked in:
> CPU: 0 UID: 0 PID: 18851 Comm: syz.0.3154 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:__pv_queued_spin_unlock_slowpath+0x223/0x2e0 kernel/locking/qspinlock_paravirt.h:504
> Code: fc ff df 48 c1 ea 03 0f b6 14 02 4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 4d 41 8b 14 24 48 8d 3d 40 00 44 05 4c 89 e6 <67> 48 0f b9 3a e9 2f ff ff ff 48 89 df 48 89 14 24 e8 17 07 e0 f6
> RSP: 0018:ffffc9000c4273a0 EFLAGS: 00010246
> RAX: 0000000000000003 RBX: ffff88802c0c8790 RCX: ffffffff8b99c87f
> RDX: 0000000000000000 RSI: ffff88802c0c8790 RDI: ffffffff90ddc8f0
> RBP: ffff88802c0c8798 R08: 0000000000000000 R09: ffffed10058190f2
> R10: ffff88802c0c8793 R11: 0000000000000000 R12: ffff88802c0c8790
> R13: ffff88802c0c8000 R14: 0000000000000000 R15: ffff88802c0c87d0
> FS:  00007ffaf56696c0(0000) GS:ffff8880d6318000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000005645e000 CR4: 0000000000352ef0
> Call Trace:
>  <TASK>
>  __raw_callee_save___pv_queued_spin_unlock_slowpath+0x15/0x40
>  .slowpath+0x9/0x18
>  pv_queued_spin_unlock arch/x86/include/asm/paravirt-spinlock.h:40 [inline]
>  queued_spin_unlock arch/x86/include/asm/paravirt-spinlock.h:72 [inline]
>  do_raw_spin_unlock+0x145/0x1e0 kernel/locking/spinlock_debug.c:142
>  __raw_spin_unlock include/linux/spinlock_api_smp.h:168 [inline]
>  _raw_spin_unlock+0x1e/0x50 kernel/locking/spinlock.c:190
>  spin_unlock include/linux/spinlock.h:390 [inline]
>  hv_tlb_flush_enqueue.isra.0+0x195/0x200 arch/x86/kvm/hyperv.c:1967
>  kvm_hv_flush_tlb+0x17b4/0x1ae0 arch/x86/kvm/hyperv.c:2150
>  kvm_hv_hypercall+0xd0b/0x2350 arch/x86/kvm/hyperv.c:2629
>  kvm_emulate_hypercall+0x115/0x3c0 arch/x86/kvm/x86.c:10510
>  __vmx_handle_exit arch/x86/kvm/vmx/vmx.c:6848 [inline]
>  vmx_handle_exit+0x4d6/0x1ef0 arch/x86/kvm/vmx/vmx.c:6858
>  vcpu_enter_guest arch/x86/kvm/x86.c:11550 [inline]
>  vcpu_run+0x3558/0x5d50 arch/x86/kvm/x86.c:11707
>  kvm_arch_vcpu_ioctl_run+0x5b6/0x1890 arch/x86/kvm/x86.c:12062
>  kvm_vcpu_ioctl+0x730/0x1700 virt/kvm/kvm_main.c:4470
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:597 [inline]
>  __se_sys_ioctl fs/ioctl.c:583 [inline]
>  __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7ffaf479ce59
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffaf5669028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007ffaf4a15fa0 RCX: 00007ffaf479ce59
> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
> RBP: 00007ffaf4832e6f R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffaf4a16038 R14: 00007ffaf4a15fa0 R15: 00007ffcc021d3a8
>  </TASK>
> ----------------
> Code disassembly (best guess), 3 bytes skipped:
>    0:	48 c1 ea 03          	shr    $0x3,%rdx
>    4:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx
>    8:	4c 89 e0             	mov    %r12,%rax
>    b:	83 e0 07             	and    $0x7,%eax
>    e:	83 c0 03             	add    $0x3,%eax
>   11:	38 d0                	cmp    %dl,%al
>   13:	7c 04                	jl     0x19
>   15:	84 d2                	test   %dl,%dl
>   17:	75 4d                	jne    0x66
>   19:	41 8b 14 24          	mov    (%r12),%edx
>   1d:	48 8d 3d 40 00 44 05 	lea    0x5440040(%rip),%rdi        # 0x5440064
>   24:	4c 89 e6             	mov    %r12,%rsi
> * 27:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
>   2c:	e9 2f ff ff ff       	jmp    0xffffff60
>   31:	48 89 df             	mov    %rbx,%rdi
>   34:	48 89 14 24          	mov    %rdx,(%rsp)
>   38:	e8 17 07 e0 f6       	call   0xf6e00754
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
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> 
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> 
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#syz test: https://github.com/sean-jc/linux.git aec262d23f20702b3fd317bf67d470499daba87a