[PATCH 3.2 142/185] KVM: Improve create VCPU parameter(CVE-2013-4587)

From: Ben Hutchings
Date: Sat Dec 28 2013 - 21:54:33 EST

3.2.54-rc1 review patch. If anyone has any objections, please let me know.


From: Andy Honig <ahonig@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Andrew Honig <ahonig@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
virt/kvm/kvm_main.c | 3 +++
1 file changed, 3 insertions(+)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1683,6 +1683,9 @@ static int kvm_vm_ioctl_create_vcpu(stru
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);

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