linux-kernel - Re: [syzbot] [kvm-x86?] WARNING in kvm_arch_vcpu_ioctl

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Message-ID: <aHkObULA-4HV2uNo@google.com>
Date: Thu, 17 Jul 2025 07:53:33 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: syzbot <syzbot+cc2032ba16cc2018ca25@...kaller.appspotmail.com>
Cc: bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, mingo@...hat.com, 
	pbonzini@...hat.com, syzkaller-bugs@...glegroups.com, tglx@...utronix.de, 
	x86@...nel.org
Subject: Re: [syzbot] [kvm-x86?] WARNING in kvm_arch_vcpu_ioctl_run (6)

On Thu, Jul 17, 2025, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    155a3c003e55 Merge tag 'for-6.16/dm-fixes-2' of git://git...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1413e58c580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8d5ef2da1e1c848
> dashboard link: https://syzkaller.appspot.com/bug?extid=cc2032ba16cc2018ca25
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1213e58c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a567d4580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-155a3c00.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/725a320dfe66/vmlinux-155a3c00.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9f06899bb6f3/bzImage-155a3c00.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+cc2032ba16cc2018ca25@...kaller.appspotmail.com
> 
> WARNING: CPU: 1 PID: 6108 at arch/x86/kvm/x86.c:11645 kvm_arch_vcpu_ioctl_run+0x13bc/0x18c0 arch/x86/kvm/x86.c:11645
> Modules linked in:
> CPU: 1 UID: 0 PID: 6108 Comm: syz.0.16 Not tainted 6.16.0-rc6-syzkaller-00002-g155a3c003e55 #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:kvm_arch_vcpu_ioctl_run+0x13bc/0x18c0 arch/x86/kvm/x86.c:11645
> Code: 0a 00 00 00 00 00 00 e8 25 88 be 1e 31 ff 89 c5 89 c6 e8 e7 68 7a 00 85 ed 0f 8f f4 f0 ff ff e9 f5 f1 ff ff e8 95 6d 7a 00 90 <0f> 0b 90 e9 9c f0 ff ff e8 87 6d 7a 00 90 0f 0b 90 e9 d3 f0 ff ff
> RSP: 0018:ffffc9000379fc38 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff888044358000 RCX: ffffffff81417587
> RDX: ffff88802327a440 RSI: ffffffff814184eb RDI: 0000000000000007
> RBP: 0000000000000001 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000001 R12: ffff88804ff02000
> R13: ffff8880443580d8 R14: 0000000000000000 R15: ffff88804ff02120
> FS:  000055555f07c500(0000) GS:ffff8880d6813000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000005200000c CR3: 0000000033cb3000 CR4: 0000000000352ef0
> Call Trace:
>  <TASK>
>  kvm_vcpu_ioctl+0x5eb/0x1690 virt/kvm/kvm_main.c:4464
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:907 [inline]
>  __se_sys_ioctl fs/ioctl.c:893 [inline]
>  __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f4f8b18e929
> 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:00007ffdc1bf8098 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007f4f8b3b5fa0 RCX: 00007f4f8b18e929
> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
> RBP: 00007f4f8b210ca1 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f4f8b3b5fa0 R14: 00007f4f8b3b5fa0 R15: 0000000000000003
>  </TASK>

Ha!  syzbot finally found an upstream reproducer:

https://lore.kernel.org/all/20250715190638.1899116-1-seanjc@google.com