From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.214.199 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793294776; b=3j+LLujL3FcOzEphvpXCdqBkyPkmbwrr1aNYpXuBey9FOiLcSnj6ATtl/QCs19tzgIMe I5BuCPk0OFjbNxAmMY0/rbYNbFd4mrqTr4UIKX1JfYbZwme0O3Uq8I8mF1GBgZvjs50Yx 2jfDoKRrxjPr4sEhIrKrCr9TMDvrXvbszpXVWvEbUB2Azg/AfUihrzqeXLIch3MY6GqY8 5ny32NT6pOC40jS+qsv0EIxw6QPxTJf3NN2MoACORF1yzRbylwykUfFwFzqvH7qwSgR8y vUY8xA23yzoubmailbtY1P9RvCE2BdgYi2Odk0+ouD8ky5IrB7565ZtJ4MY2hTBWVTQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793294776; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Received:Date:In-Reply-To: Mime-Version:References:Message-ID:Subject:From:To:Cc:Content-Type; bh=R9gXbOeTpbZuWe2yIPQcNtZrgS23nXQ+wWuvRY3jxBM=; b=3vXvRt26mJi/+wHyCF4S2gDDxZfPIgYTqubPXWdTytcyLEJxmLdxRwGRg+Q42fYB41dz NBh05EaEpL3Plr4BWyl/tfZJ4/lWrR1uGJpqkchZXot0DL7mwf15RXMY0hKVxgJm2NPnr FhNYABDAPa8WztD0ElhCQY3oqZNwlBcgGPJ/7e+lARvuoXQCPoqOevV1hTNjfsU3rTqcV Z21B5gP4DGlJvSL15V7kYvRcyUPsy0LePdBWjHVvWqbTOH4upufmpfJBXS8XyCK/ZYCVN fhl0x7M3uFAXI+u/xomQ0JZBqCr8murpOmhomk1OmGFvzlxpQPD1kp6qjPwGA+Rpd6w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=HmBo4XM0; arc=none smtp.remote-ip=209.85.214.199 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A692F606A31D for ; Thu, 29 Oct 2026 17:26:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A692F606A31D Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20260707 header.b=HmBo4XM0 Received: by mail-pl1-f199.google.com with SMTP id d9443c01a7336-2e601800e58so36942135ad.2 for ; Thu, 29 Oct 2026 10:26:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20260707; t=1793294775; x=1793899575; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=R9gXbOeTpbZuWe2yIPQcNtZrgS23nXQ+wWuvRY3jxBM=; b=HmBo4XM0keFzi449eNoOJoycWwntk7K2g7yGqHUBvxgL6z07MM2yfZ0/qhXk9Cq+/B 7yMvarlYEUpPNLYASJOwhiqgwB9jhmn382mKkF9RtloA1MjytXeJBbNDGzuch/8FwDKD 8+9WVrO/7UTllVn7k2T4v54vchjKoLO7keejckWQzYSS9uOAsccU71lJ9QN8sYtJp7qg McHY7w0cWEfJNMeiQuLhbfgAjT9rpOFaBv4YGDOJfnz780e6dn3x3yA+1duuohiR7rP8 TR/J7cFMXesT7m3RC+mNcRJZnXe86z8dax1X8slhBF4Whit2CKxWgL1JbfOLEscavRuQ XzkQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793294775; x=1793899575; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=R9gXbOeTpbZuWe2yIPQcNtZrgS23nXQ+wWuvRY3jxBM=; b=saWyMXVkWztWvmmPodF2z0/xBLZD1uOSnQigGueR5f2U3CrAKJmzl+skyqeh40OA6j BXd0ZdMYTsBKuTzO9A6/quuexMLEtt9lAFiup8EY4deGI8wvuxF/wjiUc/OYe1cuX2VR 7pjnfI/XeK/k68fw2T8eG/CA75uAX24LCM/Wruj19/dQ/Y324DKVjN98wRXlBdB35SLQ VBLdahabtHJCUwDCme8VBR7ytoXgSiFUEIcYJm9s1dYO7Gin3JxfsxGh3VXoFPHivvbN wQYpWgAvlJniu9DspXUInNZpphFGMO/pjp12gMyPSt+PRG6EQ1Ht1OJKqr2AjzWYw+TJ jw3w== X-Forwarded-Encrypted: i=1; AKwUvBxDl8TwiyhjhQmvHLa48x/qIaD2h4D+vHLZIhNFNh1K43bY+qtTc79Ne68GftzHR6BQeBMyVU9ZJf6rfDU=@vger.kernel.org X-Gm-Message-State: AFq9FYIhoXtow6Yg2IzfJ74yydROLIsichuy5bvt72nMe6mdwJj0wNEd NFoX/UwaNyFT8ooPIlZQorEUqHjSgpGibVY/S9bvUuDUeeVhpeyTDNE9QLmgeNA3O+mhen+iPrX GZGrhNg== X-Received: from pleo17.prod.google.com ([2002:a17:903:2111:b0:2e8:ab6e:81d5]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:8c4:b0:2dd:c053:a6f1 with SMTP id d9443c01a7336-2eb364e7e09mr554585ad.35.1793294774832; Thu, 29 Oct 2026 10:26:14 -0700 (PDT) Date: Thu, 29 Oct 2026 10:26:14 -0700 In-Reply-To: <6ae372ba.f57e0135.1770dd.0070.GAE@google.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 References: <6ae372ba.f57e0135.1770dd.0070.GAE@google.com> Message-ID: Subject: Re: [syzbot] [kvm?] WARNING in kvm_vcpu_ioctl From: Sean Christopherson To: syzbot Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="us-ascii" On Thu, Oct 29, 2026, syzbot wrote: > 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 > #syz dup: [syzbot] [kvm?] WARNING in kvm_vcpu_pre_fault_memory