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 9F121C433EF for ; Mon, 21 Mar 2022 16:47:24 +0000 (UTC) Received: from localhost ([::1]:56764 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nWLBj-0004nJ-NU for qemu-devel@archiver.kernel.org; Mon, 21 Mar 2022 12:47:23 -0400 Received: from eggs.gnu.org ([209.51.188.92]:37390) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nWL9Y-0002PJ-8t for qemu-devel@nongnu.org; Mon, 21 Mar 2022 12:45:08 -0400 Received: from [2a00:1450:4864:20::52c] (port=35614 helo=mail-ed1-x52c.google.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1nWL9W-00081N-FU for qemu-devel@nongnu.org; Mon, 21 Mar 2022 12:45:07 -0400 Received: by mail-ed1-x52c.google.com with SMTP id k10so4841634edj.2 for ; Mon, 21 Mar 2022 09:45:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:from:to:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=efi8DSRTf2i20NY52YUXz0KrEVCIILq2P4XhBCv2IZg=; b=Z7heLaZ7whcQFy5E86/fOscN6/fuPsbg5WOJ2eeXLP3ADu5hYFoTL2M5uSD99EjKpr iFYNVeY0rh1AfJyyLFB+8XqZKyAOZU7oPO9N9WpXcZWoR+fbOAfMdrY07i5CMi0UJdeb OgRiFoMMeDpfM6oY52ik48xVBxAPeZBd+j90v7SgExOzOtWRPD+Cnnbi1E7VOsxiAsgP DOZBmX4YO7fFu2z7sUc4P3lvNmrxiFGVyFpKRQCQvDLM7Vq0enRURQDXdkH/Vl42rWQW gdCN9sImFyhhgDX2uhMcJY98Yu4V6Amv8HGv5eq8TyA8TUbLUxbryQNz2x51dwNs+PKP vyFg== 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:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=efi8DSRTf2i20NY52YUXz0KrEVCIILq2P4XhBCv2IZg=; b=VgbbKgAvBIxR3Gm2C1CateHo7Oi08JVH+e+b0BTF/SEMCZ0mlSnkIcS1T74jxl1qrl TmK4MuQYoJA5nz0aDfeT0T3mHoyVOFBbtvTVXrwE4VwntkhydeLO4chet3IC8x4gUsL6 qRd2G1sNc97E3Iv7rk8yOMwxmI9v2oPV+t/rvPRt0x4KcVn6fe7L5hEdHW01XofpxgFt VI4dUi+rq0Pngy/lKYbrUIJ3y9UFvFxpId48xU6ScNyZh1cWQf5SoHeOmYDbGyajB44t cjhN5hDYJ7R9/+DUbMbSmNoGLlcxHU0zneUYxSBUF+UStzj9mV/uaAitkGHbCaBfdhVT Yovw== X-Gm-Message-State: AOAM530BDyQXnpCMgq91aufDGeo3p7DFqr2HBPQ5ugeUXUOc8HxZvr0z 63MmxaueefVuME+S253TDfyz3c0Q+qc= X-Google-Smtp-Source: ABdhPJwWKREyySZf771JABKj0wk//ydliDWWNVluKijobp/S/9c2c4u1su8j9NsaVq0BJ9+M8hrHrg== X-Received: by 2002:a05:6402:17dc:b0:418:efa5:f445 with SMTP id s28-20020a05640217dc00b00418efa5f445mr23805286edy.125.1647881105154; Mon, 21 Mar 2022 09:45:05 -0700 (PDT) Received: from avogadro.redhat.com ([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id a102-20020a509eef000000b0041614c8f79asm7949352edf.88.2022.03.21.09.45.04 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Mar 2022 09:45:04 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 1/2] target/i386: kvm: do not access uninitialized variable on older kernels Date: Mon, 21 Mar 2022 17:45:01 +0100 Message-Id: <20220321164502.201160-2-pbonzini@redhat.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220321164502.201160-1-pbonzini@redhat.com> References: <20220321164502.201160-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::52c (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::52c; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x52c.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: , 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 --- 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