WARNING in x86_emulate_insn (2)

Status: upstream: reported C repro on 2025/11/24 14:40
Subsystems: kvm-x86
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+fa52a184ebce1b30ad49@syzkaller.appspotmail.com
First crash: 345d, last: 6d21h
Cause bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
f119e19e assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ✅ VMHostTrigger: ❌ ❓ WARNING in x86_emulate_insn (2) 2026/05/22 08:46 2026/05/22 08:46 2026/05/22 10:06 70ae9b03
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly kvm-x86 report (Oct 2026) 0 (1) 2026/10/15 04:33
[syzbot] [kvm-x86?] WARNING in x86_emulate_insn (2) 1 (3) 2025/11/24 21:13
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-12 WARNING in x86_emulate_insn origin:upstream -1 syz 2 10d 247d 0/1 premoderation: reported syz repro on 2026/03/03 07:34
upstream WARNING in x86_emulate_insn kvm-x86 -1 syz, C error 309 3210d 3256d 0/29 closed as invalid on 2019/11/07 10:18
▶ ▼ Last patch testing requests (11)
Created Duration User Patch Repo Result
2026/10/15 02:30 33m retest repro linux-next report job log log
2026/08/05 12:08 11m retest repro linux-next error
2026/06/23 20:38 24m retest repro upstream no crash log
2026/05/26 13:14 31m retest repro linux-next error
2026/04/27 18:53 32m retest repro linux-next no crash log
2026/04/27 17:41 1h18m retest repro linux-next no crash log
2026/03/17 12:43 17m retest repro linux-next report log
2026/02/16 13:21 40m retest repro linux-next report log
2026/02/16 13:12 31m retest repro linux-next report log
2025/12/08 11:27 38m retest repro linux-next report log
2025/11/24 20:20 23m seanjc@google.com https://github.com/sean-jc/linux.git x86/emulator_no_avx report log

Sample crash report:
------------[ cut here ]------------
__ret
WARNING: arch/x86/kvm/emulate.c:5569 at x86_emulate_insn+0x2ad0/0x4350 arch/x86/kvm/emulate.c:5569, CPU#0: syz-executor536/6085
Modules linked in:
CPU: 0 UID: 0 PID: 6085 Comm: syz-executor536 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:x86_emulate_insn+0x2ad0/0x4350 arch/x86/kvm/emulate.c:5569
Code: 36 31 ff 44 89 f6 e8 ff 46 7f 00 45 85 f6 0f 84 0d 02 00 00 e8 e1 41 7f 00 41 bd 01 00 00 00 e9 ab f8 ff ff e8 d1 41 7f 00 90 <0f> 0b 90 48 8b 44 24 40 42 80 3c 38 00 74 08 4c 89 e7 e8 b9 15 f6
RSP: 0018:ffffc90005ee7900 EFLAGS: 00010293
RAX: ffffffff8149d21f RBX: 000304000010220a RCX: ffff888032ce9f40
RDX: 0000000000000000 RSI: 00000000000000ff RDI: 000000000000001f
RBP: ffffc90005ee7a10 R08: ffff888032ce9f40 R09: 0000000000000002
R10: 0000000000000006 R11: 0000000000000000 R12: ffff88807abcc5c8
R13: ffff88807abcc5c0 R14: 00000000000000ff R15: dffffc0000000000
FS:  00007f612f4e56c0(0000) GS:ffff888123620000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000078cf0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 x86_emulate_instruction+0xf56/0x1e90 arch/x86/kvm/x86.c:6524
 kvm_arch_vcpu_ioctl_run+0x114d/0x18b0 arch/x86/kvm/x86.c:9047
 kvm_vcpu_ioctl+0xa61/0xfd0 virt/kvm/kvm_main.c:4575
 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:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f612f50f2d9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f612f4e51d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f612f5c3b48 RCX: 00007f612f50f2d9
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 00007f612f5c3b40 R08: 36203a6b63617473 R09: 36203a6b63617473
R10: 36203a6b63617473 R11: 0000000000000246 R12: 00007f612f5933b8
R13: 000000200000aba7 R14: 00002000000001d0 R15: 00002000000001c0
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/29 11:56 upstream c339f4010dea b1d00f76 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in x86_emulate_insn
2026/10/22 18:51 linux-next bd1ecbb61afe 4ba27f85 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in x86_emulate_insn
2026/03/03 09:13 linux-next d517cb8cea01 28b83e23 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in x86_emulate_insn
2026/06/09 18:48 upstream 2d3090a8aeb5 c36c07f6 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in x86_emulate_insn
2025/11/24 10:36 linux-next d724c6f85e80 4fb8ef37 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in x86_emulate_insn
* Struck through repros no longer work on HEAD.