[PATCH 3.16 62/72] KVM: x86: fix out-of-bounds write in KVM_GET_EMULATED_CPUID (CVE-2019-19332)

Ben Hutchings
2019-12-08T13:55:29Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit 433f4ba1904100da65a311033f17a9bf586b287e upstream.

The bounds check was present in KVM_GET_SUPPORTED_CPUID but not
KVM_GET_EMULATED_CPUID.

Reported-by: syzbot+e3f4897236c4eeb8af4f@syzkaller.appspotmail.com
Fixes: 84cffe499b94 ("kvm: Emulate MOVBE", 2013-10-29)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/kvm/cpuid.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -327,7 +327,7 @@ static inline int __do_cpuid_ent(struct

r = -E2BIG;

- if (*nent >= maxnent)
+ if (WARN_ON(*nent >= maxnent))
goto out;

do_cpuid_1_ent(entry, function, index);
@@ -599,6 +599,9 @@ out:
static int do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 func,
u32 idx, int *nent, int maxnent, unsigned int type)
{
+ if (*nent >= maxnent)
+ return -E2BIG;
+
if (type == KVM_GET_EMULATED_CPUID)
return __do_cpuid_ent_emulated(entry, func, idx, nent, maxnent);