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 3.0-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-3.0 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
@@ -1539,6 +1539,11 @@ 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-3.0/kvm-x86-convert-msr_kvm_system_time-to-use-gfn_to_hva_cache-functions-cve-2013-1797.patch
queue-3.0/kvm-x86-fix-for-buffer-overflow-in-handling-of-msr_kvm_system_time-cve-2013-1796.patch
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