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 5BA95C433F5 for ; Fri, 18 Mar 2022 15:40:49 +0000 (UTC) Received: from localhost ([::1]:45402 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nVEic-00013T-TM for qemu-devel@archiver.kernel.org; Fri, 18 Mar 2022 11:40:48 -0400 Received: from eggs.gnu.org ([209.51.188.92]:46436) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nVEUq-0007e3-Uz for qemu-devel@nongnu.org; Fri, 18 Mar 2022 11:26:32 -0400 Received: from [2a00:1450:4864:20::532] (port=42703 helo=mail-ed1-x532.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nVEUp-0006JA-7v for qemu-devel@nongnu.org; Fri, 18 Mar 2022 11:26:32 -0400 Received: by mail-ed1-x532.google.com with SMTP id a17so9634261edm.9 for ; Fri, 18 Mar 2022 08:26:30 -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=5jfDVQHwgo4EPYTqpsajJCrkiZ7vbTgW4mqRzuRwUJo=; b=Z02NNApgeP06w0uqfjN4qedDFAA3Q0MYdrR40VNVhQTJJ4D8Tai1X70u86McrGTXOy EPR4aETXt7CiqJCAF7LClZZ+Xl8/AGpbQXTLDQKKd1WZuTsx7xC9XoOtkemBUvnJDM2R 3HuyKKuX+KSAlaHlpGaj9ks+dBNea+1oG7b1hocEbimMN84C5vUjGLoeLe3XgZjwhBnd 4JlDN99J5PvhKLvbA/A//qVHXjrb1gi0uOQYodeZvrFpi8aSOGSLnGOhMZE42jQ5GeLO QQ6k+sA7hhFpg5gMaHrxvwIS0PpCYY/XLLcsVLP2sx1XLllJD1XNW4RKNzvFLwzjuUpb U2CA== 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=5jfDVQHwgo4EPYTqpsajJCrkiZ7vbTgW4mqRzuRwUJo=; b=Bdp0jCavWhpxlekxwaj+JAp3LJg1C+RZvSArhLlJI2+Iv+LeGTkrKL3Q/tV/QtEJj0 lZ53j4M++TwaGDOoE89hzkDDnWgYqHaJ/YSyQRKOsuWZnZH1kwmcWHxSAiYbmt95LTFy FWbnAlkKQKM0/IaKUgNsqrC7WR4sRy2szM2koUetplxdmSx17qMC94KG5D4dY+4mAKF2 1hMf/mPPaSbJJCkkEpFafUHC3JLjTNb18H5OE5HS7AaVfWmSgaFe8Sk3yAar0qoknQLC epz3f5Frzj5eXh7BvFy1tl2oxIQadXX2f8U/HvWPFjDmc28LeNy+bQQHAR/8/P8If7lr zXNA== X-Gm-Message-State: AOAM5331Ld+JsFXucbHu85uYS6xYOGAELHVd5Q5BIypvyTcryc86w1ym /XZZktGhkIfX/+GN6p0H1FD03SGuV1s= X-Google-Smtp-Source: ABdhPJyqp+l5gN7Os6F7cWYCh0rKL3hxfXVOyUVmKTjhxmyPH4IbCXWetMmKBS/ZEWZQovtr+1LS8g== X-Received: by 2002:a05:6402:4386:b0:416:9ea3:5ee2 with SMTP id o6-20020a056402438600b004169ea35ee2mr10036089edc.298.1647617188859; Fri, 18 Mar 2022 08:26:28 -0700 (PDT) Received: from avogadro.lan ([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id s4-20020a170906a18400b006db0a78bde8sm3837539ejy.87.2022.03.18.08.26.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Mar 2022 08:26:28 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PATCH] target/i386: kvm: do not access uninitialized variable on older kernels Date: Fri, 18 Mar 2022 16:26:26 +0100 Message-Id: <20220318152626.165431-1-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::532 (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::532; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x532.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 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. While at it, explain why the ioctl is needed and KVM_GET_SUPPORTED_CPUID is not enough. Signed-off-by: Paolo Bonzini --- 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 ce0e8a4042..f2c9f7b5ca 100644 --- a/target/i386/kvm/kvm.c +++ b/target/i386/kvm/kvm.c @@ -412,6 +412,12 @@ 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, @@ -420,13 +426,16 @@ 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 == -1) { + if (errno != 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