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Thu, 29 Oct 2026 09:22:18 -0700 (PDT) Date: Thu, 29 Oct 2026 09:22:18 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ae372ba.f57e0135.1770dd.0070.GAE@google.com> Subject: [syzbot] [kvm?] WARNING in kvm_vcpu_ioctl From: syzbot To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: c339f4010dea Merge tag 'platform-drivers-x86-v7.4-1' of gi.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15f440b1580000 kernel config: https://syzkaller.appspot.com/x/.config?x=119e5f4d0a8d39cf dashboard link: https://syzkaller.appspot.com/bug?extid=da2a2f350196c7a0a389 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=12952929580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c339f401.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/ff23ecfc810c/vmlinux-c339f401.xz kernel image: https://storage.googleapis.com/syzbot-assets/6554a89077aa/bzImage-c339f401.xz AI-generated root cause summary: When a VM is terminated or marked dead (e.g., via kvm_vm_dead() due to an error in enter_smm() or migration), the KVM_REQ_VM_DEAD request is raised on its vCPUs. If userspace subsequently issues the KVM_PRE_FAULT_MEMORY ioctl, kvm_tdp_page_prefault() bails out upon observing KVM_REQ_VM_DEAD and returns -EIO. However, kvm_vcpu_pre_fault_memory() in virt/kvm/kvm_main.c considers -EIO an unexpected internal condition and triggers WARN_ON_ONCE(r == 0 || r == -EIO). In a production kernel without panic_on_warn, execution breaks out of the loop and cleanly returns -EIO to userspace without crashing or corrupting memory. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=da2a2f350196c7a0a389 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+da2a2f350196c7a0a389@syzkaller.appspotmail.com ------------[ cut here ]------------ r == 0 || r == -EIO WARNING: arch/x86/kvm/../../../virt/kvm/kvm_main.c:4465 at kvm_vcpu_pre_fault_memory virt/kvm/kvm_main.c:4465 [inline], CPU#1: syz.0.17/6063 WARNING: arch/x86/kvm/../../../virt/kvm/kvm_main.c:4465 at kvm_vcpu_ioctl+0x156a/0x17b0 virt/kvm/kvm_main.c:4744, CPU#1: syz.0.17/6063 Modules linked in: CPU: 1 UID: 0 PID: 6063 Comm: syz.0.17 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:kvm_vcpu_pre_fault_memory virt/kvm/kvm_main.c:4465 [inline] RIP: 0010:kvm_vcpu_ioctl+0x156a/0x17b0 virt/kvm/kvm_main.c:4744 Code: 9c 35 8b 00 be 01 00 00 00 4c 89 f7 e8 4f b1 b5 03 e9 c3 f8 ff ff e8 85 35 8b 00 90 0f 0b 90 e9 2c f2 ff ff e8 77 35 8b 00 90 <0f> 0b 90 e9 38 fd ff ff e8 69 35 8b 00 65 48 8b 3d 99 02 36 14 31 RSP: 0018:ffffc90003957c98 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 1ffff9200072af98 RCX: 0000000000000000 RDX: ffff8880355fcb00 RSI: ffffffff81831d69 RDI: 0000000000000007 RBP: ffff8880459f8048 R08: fffffffffffffffb R09: fffffffffffffffb R10: ffff8880459f803f R11: 0000000000000001 R12: fffffffffffffffb R13: ffffed1006abf960 R14: ffff8880459f8000 R15: ffffc90003957d70 FS: 00007f7bf8c946c0(0000) GS:ffff8880d458e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0b9aa1ee9c CR3: 0000000037636000 CR4: 0000000000352ef0 Call Trace: 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:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f7bf7d9f559 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:00007f7bf8c94028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f7bf8026090 RCX: 00007f7bf7d9f559 RDX: 0000200000000800 RSI: 00000000c040aed5 RDI: 0000000000000005 RBP: 00007f7bf7e36b20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f7bf8026128 R14: 00007f7bf8026090 R15: 00007ffcdd24ea18 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup