From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 28F6CC433EF for ; Sun, 20 Mar 2022 19:40:01 +0000 (UTC) Received: from localhost ([::1]:36890 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nW1PE-0004xF-82 for qemu-devel@archiver.kernel.org; Sun, 20 Mar 2022 15:40:00 -0400 Received: from eggs.gnu.org ([209.51.188.92]:56944) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nW1Ob-0004HQ-QW for qemu-devel@nongnu.org; Sun, 20 Mar 2022 15:39:21 -0400 Received: from [2a00:1450:4864:20::62d] (port=34609 helo=mail-ej1-x62d.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nW1Oa-0004XA-7Z for qemu-devel@nongnu.org; Sun, 20 Mar 2022 15:39:21 -0400 Received: by mail-ej1-x62d.google.com with SMTP id o10so7412801ejd.1 for ; Sun, 20 Mar 2022 12:39:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=meXKtiTj9oVaBUBtAhQzlAyITdYiehVjmV1emt2Kta0=; b=aP6DPVVyuNe3pB5LM+VwbmJoLcB7UMOQr+F3mfmDU9woF5C2mJ6IQJc+TeBq1TGKWn BRyJsWkq6tA+v+uytk0FpD0PF1usStqFYJwWOepjFeVjf+tiFQyZYsvgAjuSwoMWkhAZ rPyf2mXk0dYjjHCthrUb4lYkKInkly7pK2w1s/fFTfNOhQ1ofbV+OI35+ZeP+ZAt3+uj O56oV6ACf6SrHay7/OCrtgr1Ueth0aExZGUTqv89guoa6XuZhTjws1zujQoOWzWo7JrB gHnJQ8aASX0r2XoKCXYG6qiE2xL2dtbunDCmfKrqomMxoQF7I25+qT6z9EvMiQCyv0AN 5DiQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :mime-version:content-transfer-encoding; bh=meXKtiTj9oVaBUBtAhQzlAyITdYiehVjmV1emt2Kta0=; b=rxdhmm0sA7SY4KoRVOrTsPy1AixOrSF7popjwXvbQ45tE17t5f2fBkNAt6k79sL3bM Iik5cP8NqCG4rdzzoRgNOZ3dfnGw0oZUk2EYyiX6/yxNpPeuk+BitdswwdA8EOmcp+LY /wT7LPC2sXfSSdnauUP0XE/MIidaSFwk9cbt+fFHE7jPg+TwepwLUHqPsP1J7IOr8oX/ icNgrWPm2tBlAE+DmR+0mq1KMyOYipuEcU4QFJfiQ7UqCjphZJiusTqBRh0icHaFjuS9 ekoniXug/kX3qT5EvK2PwWQTIpglDZuRrf+MgBtSWO0iHLLgaMJwcLYUMVkv7TJVM7rQ QMqw== X-Gm-Message-State: AOAM532rMYOXltu6UE9HmZCXxfsmQAajJOoHgryuElRCbTPK7r9hSJnJ CBL65ARy8upB8we/pRgqvrpzZC0a7qQ= X-Google-Smtp-Source: ABdhPJx9EsGHCeoDggkD7JO8NrIg0QThpimHMdTIh1t5wh09KRRBLft0RTsO6oa610sWaVR2B2bq8A== X-Received: by 2002:a17:906:2b93:b0:6cf:bb48:5a80 with SMTP id m19-20020a1709062b9300b006cfbb485a80mr17341032ejg.681.1647805158125; Sun, 20 Mar 2022 12:39:18 -0700 (PDT) Received: from avogadro.lan ([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id i11-20020a50fd0b000000b0041936bc0f7esm815116eds.52.2022.03.20.12.39.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Mar 2022 12:39:17 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PATCH v2] target/i386: kvm: do not access uninitialized variable on older kernels Date: Sun, 20 Mar 2022 20:39:14 +0100 Message-Id: <20220320193914.111356-1-pbonzini@redhat.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::62d (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::62d; envelope-from=paolo.bonzini@gmail.com; helo=mail-ej1-x62d.google.com X-Spam_score_int: 0 X-Spam_score: -0.1 X-Spam_bar: / X-Spam_report: (-0.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, PDS_HP_HELO_NORDNS=0.659, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pkrempa@redhat.com, vr_qemu@t-online.de Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" KVM support for AMX includes a new system attribute, KVM_X86_XCOMP_GUEST_SUPP. Commit 19db68ca68 ("x86: Grant AMX permission for guest", 2022-03-15) however did not fully consider the behavior on older kernels. First, it warns too aggressively. Second, it invokes the KVM_GET_DEVICE_ATTR ioctl unconditionally and then uses the "bitmask" variable, which remains uninitialized if the ioctl fails. Third, kvm_ioctl returns -errno rather than -1 on errors. While at it, explain why the ioctl is needed and KVM_GET_SUPPORTED_CPUID is not enough. Signed-off-by: Paolo Bonzini --- v1->v2: for error condition for kvm_ioctl [Volker] target/i386/kvm/kvm.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c index ef2c68a6f4..06901c2a43 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -411,6 +411,12 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, } } else if (function == 0xd && index == 0 && (reg == R_EAX || reg == R_EDX)) { + /* + * The value returned by KVM_GET_SUPPORTED_CPUID does not include + * features that still have to be enabled with the arch_prctl + * system call. QEMU needs the full value, which is retrieved + * with KVM_GET_DEVICE_ATTR. + */ struct kvm_device_attr attr = { .group = 0, .attr = KVM_X86_XCOMP_GUEST_SUPP, @@ -419,13 +425,16 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, bool sys_attr = kvm_check_extension(s, KVM_CAP_SYS_ATTRIBUTES); if (!sys_attr) { - warn_report("cannot get sys attribute capabilities %d", sys_attr); + return ret; } int rc = kvm_ioctl(s, KVM_GET_DEVICE_ATTR, &attr); - if (rc == -1 && (errno == ENXIO || errno == EINVAL)) { - warn_report("KVM_GET_DEVICE_ATTR(0, KVM_X86_XCOMP_GUEST_SUPP) " - "error: %d", rc); + if (rc < 0) { + if (rc != -ENXIO) { + warn_report("KVM_GET_DEVICE_ATTR(0, KVM_X86_XCOMP_GUEST_SUPP) " + "error: %d", rc); + } + return ret; } ret = (reg == R_EAX) ? bitmask : bitmask >> 32; } else if (function == 0x80000001 && reg == R_ECX) { -- 2.35.1