Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967203Ab3DRJ37 (ORCPT ); Thu, 18 Apr 2013 05:29:59 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:40155 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757412Ab3DRJRz (ORCPT ); Thu, 18 Apr 2013 05:17:55 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Andrew Honig , Marcelo Tosatti , Luis Henriques Subject: [PATCH 34/72] KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796) Date: Thu, 18 Apr 2013 10:16:19 +0100 Message-Id: <1366276617-3553-35-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1366276617-3553-1-git-send-email-luis.henriques@canonical.com> References: <1366276617-3553-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1746 Lines: 49 3.5.7.11 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Honig commit c300aa64ddf57d9c5d9c898a64b36877345dd4a9 upstream. If the guest sets the GPA of the time_page so that the request to update the time straddles a page then KVM will write onto an incorrect page. The write is done byusing kmap atomic to get a pointer to the page for the time structure and then performing a memcpy to that page starting at an offset that the guest controls. Well behaved guests always provide a 32-byte aligned address, however a malicious guest could use this to corrupt host kernel memory. Tested: Tested against kvmclock unit test. Signed-off-by: Andrew Honig Signed-off-by: Marcelo Tosatti Signed-off-by: Luis Henriques --- arch/x86/kvm/x86.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8b6fbee..ad5cf4b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1618,6 +1618,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) /* ...but clean it before doing the actual write */ vcpu->arch.time_offset = data & ~(PAGE_MASK | 1); + /* Check that the address is 32-byte aligned. */ + if (vcpu->arch.time_offset & + (sizeof(struct pvclock_vcpu_time_info) - 1)) + break; + vcpu->arch.time_page = gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT); -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/