linux-kernel - Re: [syzbot] [kvm-x86?] WARNING in x86_emulate

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Message-ID: <6924ca5e.a70a0220.d98e3.0097.GAE@google.com>
Date: Mon, 24 Nov 2025 13:13:02 -0800
From: syzbot <syzbot+fa52a184ebce1b30ad49@...kaller.appspotmail.com>
To: 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, seanjc@...gle.com, syzkaller-bugs@...glegroups.com, 
	tglx@...utronix.de, x86@...nel.org
Subject: Re: [syzbot] [kvm-x86?] WARNING in x86_emulate_insn (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in x86_emulate_insn

------------[ cut here ]------------
WARNING: arch/x86/kvm/emulate.c:5433 at x86_emulate_insn+0x265f/0x3bd0 arch/x86/kvm/emulate.c:5433, CPU#0: syz.2.670/9601
Modules linked in:
CPU: 0 UID: 0 PID: 9601 Comm: syz.2.670 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:x86_emulate_insn+0x265f/0x3bd0 arch/x86/kvm/emulate.c:5433
Code: 00 41 8b 2e 31 ff 89 ee e8 ee 83 77 00 85 ed 0f 84 f4 01 00 00 e8 a1 7f 77 00 bd 01 00 00 00 e9 9d f9 ff ff e8 92 7f 77 00 90 <0f> 0b 90 48 8b 44 24 28 42 80 3c 28 00 74 08 4c 89 e7 e8 7a 1b de
RSP: 0018:ffffc90003327748 EFLAGS: 00010293
RAX: ffffffff814a79de RBX: ffff888027c7e270 RCX: ffff88802f2abd00
RDX: 0000000000000000 RSI: 00000000000000ff RDI: 000000000000001f
RBP: 00000000000000ff R08: ffff88802f2abd00 R09: 0000000000000002
R10: 0000000000000006 R11: 0000000000000000 R12: ffff888027c7e278
R13: dffffc0000000000 R14: ffff888027c7e2a0 R15: 0000000000000000
FS:  00007fd173f646c0(0000) GS:ffff888125a6f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007741a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 x86_emulate_instruction+0xea7/0x20b0 arch/x86/kvm/x86.c:9512
 kvm_arch_vcpu_ioctl_run+0x1404/0x1cd0 arch/x86/kvm/x86.c:11951
 kvm_vcpu_ioctl+0x99a/0xed0 virt/kvm/kvm_main.c:4477
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd17318f749
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:00007fd173f64038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd1733e6090 RCX: 00007fd17318f749
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00007fd173213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd1733e6128 R14: 00007fd1733e6090 R15: 00007ffe5ab25448
 </TASK>


Tested on:

commit:         380ecf40 Revert "KVM: x86: Add support for emulating M..
git tree:       https://github.com/sean-jc/linux.git x86/emulator_no_avx
console output: https://syzkaller.appspot.com/x/log.txt?x=155af97c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=763fb984aa266726
dashboard link: https://syzkaller.appspot.com/bug?extid=fa52a184ebce1b30ad49
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.