From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A693621ABD7 for ; Wed, 9 Apr 2025 20:41:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744231304; cv=none; b=BNvpRUXZMmHa8MxSYw2xiLrHq+CMgJ5hwLsg8sfYsa4+vXt4ry28Do2ObM+bAoSfEF5Awdf4P/7WlaKqX897c7392hTC9BkROnFXO34bmqA2v9wqX4ji3GttxMkeyiJmKLiNLCrMLzmlA6UZGDV5gu/Hckby1Bl882peGix2QCk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744231304; c=relaxed/simple; bh=3wiKPK3bBwkcZ2R2S9JuygT1liPdoEqLtKvDn4cR2SQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=ceRAPuVMagsz8t2S4Ib5vhDbP0XXxU/d+LJqRxqlgKsHaR34IIPd+tf+m21UD3ej7YLSicrwHqBWwXhFJyalfcdMGGOuosMp+bS5ab9ps7sgJ9u1II4h/CLzmRAIQ1QTKjipW02z8kUXAUPE6r9oUDwP9Y9dthkEVgsYu9LeDoI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=sTAO08+/; arc=none smtp.client-ip=209.85.210.201 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) header.d=google.com header.i=@google.com header.b="sTAO08+/" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-736b2a25d9fso36915b3a.0 for ; Wed, 09 Apr 2025 13:41:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1744231302; x=1744836102; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=ieoIvphqiGbAKMBpBQheDMztn7Ma+D+YzJ22q+cnEVc=; b=sTAO08+/3WY6epr3PWK3Pzda8vG9F7oi97LW7o3rAeIIajIeLqfgbBhrJpYAPDfTea JUyTn6Rem73zK2eNc/uNAO32CCRGnWhfqfRv9c+WrAzkH392r6vYJom/bWn5Ue1Viles t3D/XCbpe9Wdyh1Mo7FYyXvpjnpHwckXP+YeDsfMiQBgvrCEaJcEeDAtvZoVnR7ddRQ1 tf2uMfpa28qweyLc92rorTc234aZZek5GDV97G7ng9ap+D4hi+2pFUbrJpdZkbNlHDAo gbJmwd1IRZLoBrAmJrDlbtjISYcp0KBmPtmCnLjRYEbcadl8/UjJiA+DdPedD4GDYaGY DVtQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744231302; x=1744836102; h=content-transfer-encoding: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; bh=ieoIvphqiGbAKMBpBQheDMztn7Ma+D+YzJ22q+cnEVc=; b=NCQgNMRAImaHR465AzUEqFLuSkkFS1DtEZyLCvBHrLinTVsNC0TyvK6/qoIrp8YC/v 15sZA8NXYhdfp1ArBcUi3GlaEXj3LOhaFw81zNvhGkG7Bx0cLXsIUjQ1j9xGD5SUdxAu bZPcQSyyhIL0KMRYiRzBrmBIr9cKLR7/v3ounVhaE6nx9FC/DNJ4Oipy+1fb4SzvzlnQ jbINBHDEwoR6lT0DvV4GaTcnIyExGCp7IagLVjzgQs4UZriuQbwyIvop3Zu9K0BCGWz7 2q6u5SBVkuO88f92tjyRFNqGT1lwyttHOvaIsP4u9AvktGhY4vwnYHGW3rF3gY886hog NisA== X-Forwarded-Encrypted: i=1; AJvYcCXhN6fihxPGR15jq1DHkJaU7VbQ3VZMHII1peg9phDYwGWgjCsD5iPKWD2wbdrQcVpJIQA=@vger.kernel.org X-Gm-Message-State: AOJu0YyUa6bdfwRFSklfyyvmDG7tLLDgHZc5jmw//qTCSaqRRVYKeem5 qJ6eu2YS1bav8l0ULf1WoQVI+t3X2QlBv9wrDT9qI55499FUyZGnCzzjsmq2951wVSMvv54XpP6 h5A== X-Google-Smtp-Source: AGHT+IFydrkQXn90pkKPYhdpK0P18a0JZkMT6KtxrVusmlyKG0vy9rQQutHGFxIj8bezVw2sQfCI6eVl1us= X-Received: from pfbkq7.prod.google.com ([2002:a05:6a00:4b07:b0:736:ab5f:21f4]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:728b:b0:1f5:6f61:a0ac with SMTP id adf61e73a8af0-2016946066amr716605637.5.1744231301902; Wed, 09 Apr 2025 13:41:41 -0700 (PDT) Date: Wed, 9 Apr 2025 13:41:40 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: Message-ID: Subject: Re: [Confusing Bug] A Long-running Syzkaller Docker Crashes Host System From: Sean Christopherson To: Zhiyu Zhang Cc: pbonzini@redhat.com, syzkaller , kvm@vger.kernel.org, tglx@linutronix.de Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wed, Apr 09, 2025, Zhiyu Zhang wrote: > Dear Syzkaller Group and Linux Kernel Upstream, >=20 > I am writing to report an intermittent issue that appears when running > Syzkaller inside a Docker container with privileged KVM access. The > host system becomes unresponsive after prolonged fuzzing, and I hope > your insights can help identify the root cause. >=20 > Environment Details: > - Host Machine: > - OS: Ubuntu 20.04.6 LTS > - Kernel: x86_64 Linux 5.15.0-136-generic > - CPU: Intel Xeon Platinum 8268 @ 192=C3=973.9GHz > - Docker Container: > - Base Image: Ubuntu 22.04 (qgrain/kernel-fuzz:v1) > - Syzkaller Version: commit 4121cf9 (20250217) > - Startup Command: docker run -itd -p 29400:22 -v > /PATH/KERNELS:/root/kernels --name NAME --privileged=3Dtrue > qgrain/kernel-fuzz:v1 >=20 > After the fuzzing instances had been running for an extended period, > the host system became completely inaccessible (e.g., SSH connections > failed). Through IPMI, I observed the following repeated log messages > on the virtual terminal: You'll likely need some way to get more information about the state of the = host kernel when things go sideways. E.g. force a crash and get a kdump. Eithe= r that, or hope you get lucky and capture an oops/panic. > [244053.888249] kvm [3867]: vcpu2, guest pF: 0xffffffff813008ac > vmx_set_jsr: BTF ln_inA2_DEBUGTRLSR 0x2, nop > [244053.938264] kvm [3867]: vcpu3, guest pF: 0xffffffff813008ac > vmx_set_jsr: BTF ln_inA2_DEBUGTRLSR 0x2, nop > [244053.960191] kvm [3867]: vcpu0, guest pF: 0xffffffff813008ac > vmx_set_jsr: BTF ln_inA2_DEBUGTRLSR 0x2, nop > [244053.992411] kvm [3867]: vcpu1, guest pF: 0xffffffff813008ac > vmx_set_jsr: BTF ln_inA2_DEBUGTRLSR 0x2, nop > [244075.149293] kvm [3882]: vcpu3, guest pF: 0xffffffff81300744 > vmx_set_jsr: BTF ln_inA2_DEBUGTRLSR 0x2, nop What is producing these messages? It's not the upstream kernel. If your s= ystem is generating gobs of logging, it's entirely possible the logging itself is causing problems. > ... >=20 > Speculation on Possible Causes: > - One possibility is that the long-term Syzkaller fuzzing workload has > generated test cases that trigger an edge-case bug in the host KVM > module. The repeated =E2=80=9Cguest pF=E2=80=9D errors could indicate tha= t a specific > sequence of guest instructions is not being handled correctly. > - Alternatively, prolonged high-load conditions from continuous > fuzzing might have exposed an unhandled kernel or hardware bug related > to virtualization=E2=80=94potentially in the CPU=E2=80=99s VMX or within = the KVM > module itself. >=20 > I apologize for the limited diagnostic information available at this > time (find nothing relevant to KVM in system logs). The above > speculation is preliminary, and I am unsure whether the root cause > lies within the Syzkaller side or Kernel KVM side. >=20 > Thank you for your attention to this matter. I look forward to any > suggestions or questions you may have. >=20 > Best regards, > Zhiyu Zhang