From: Andy Honig <ahonig@google.com>
Date: Tue, 19 Nov 2013 00:09:22 +0000 (-0800)
Subject: KVM: Improve create VCPU parameter (CVE-2013-4587)
X-Git-Tag: v3.2.54~44
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=4a94970b318e0d7387c2d84fa7c92ea782ae52b3

KVM: Improve create VCPU parameter (CVE-2013-4587)

commit 338c7dbadd2671189cec7faf64c84d01071b3f96 upstream.

In multiple functions the vcpu_id is used as an offset into a bitfield.  Ag
malicious user could specify a vcpu_id greater than 255 in order to set or
clear bits in kernel memory.  This could be used to elevate priveges in the
kernel.  This patch verifies that the vcpu_id provided is less than 255.
The api documentation already specifies that the vcpu_id must be less than
max_vcpus, but this is currently not checked.

Reported-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8bf05f055c0a..bfa8e1e75a48 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1683,6 +1683,9 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
 	int r;
 	struct kvm_vcpu *vcpu, *v;
 
+	if (id >= KVM_MAX_VCPUS)
+		return -EINVAL;
+
 	vcpu = kvm_arch_vcpu_create(kvm, id);
 	if (IS_ERR(vcpu))
 		return PTR_ERR(vcpu);