KVM: Prevent overflow in KVM_GET_SUPPORTED_CPUID

The number of entries is multiplied by the entry size, which can
overflow on 32-bit hosts.  Bound the entry count instead.

Reported-by: David Wagner <daw@cs.berkeley.edu>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ffccb5c85d60eebb63952fff4a2fa07fcde1beb0..b2f4f13bf4a1e3c8a0e42fac1bd7c3de7adf6a21 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1593,6 +1593,8 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
 
        if (cpuid->nent < 1)
                goto out;
+       if (cpuid->nent > KVM_MAX_CPUID_ENTRIES)
+               cpuid->nent = KVM_MAX_CPUID_ENTRIES;
        r = -ENOMEM;
        cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry2) * cpuid->nent);
        if (!cpuid_entries)