This is a note to let you know that I've just added the patch titled KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796) to the 3.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-x86-fix-for-buffer-overflow-in-handling-of-msr_kvm_system_time-cve-2013-1796.patch and it can be found in the queue-3.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From c300aa64ddf57d9c5d9c898a64b36877345dd4a9 Mon Sep 17 00:00:00 2001 From: Andy Honig <ahonig@xxxxxxxxxx> Date: Mon, 11 Mar 2013 09:34:52 -0700 Subject: KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796) From: Andy Honig <ahonig@xxxxxxxxxx> 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 <ahonig@xxxxxxxxxx> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> Cc: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/x86.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1960,6 +1960,11 @@ int kvm_set_msr_common(struct kvm_vcpu * /* ...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); Patches currently in stable-queue which might be from ahonig@xxxxxxxxxx are queue-3.8/kvm-allow-cross-page-reads-and-writes-from-cached-translations.patch queue-3.8/kvm-fix-bounds-checking-in-ioapic-indirect-register-reads-cve-2013-1798.patch queue-3.8/kvm-x86-convert-msr_kvm_system_time-to-use-gfn_to_hva_cache-functions-cve-2013-1797.patch queue-3.8/kvm-x86-fix-for-buffer-overflow-in-handling-of-msr_kvm_system_time-cve-2013-1796.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html