From 433f4ba1904100da65a311033f17a9bf586b287e Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 4 Dec 2019 10:28:54 +0100 Subject: [PATCH] KVM: x86: fix out-of-bounds write in KVM_GET_EMULATED_CPUID (CVE-2019-19332) 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 --- arch/x86/kvm/cpuid.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 813a4d2e5c0c..cfafa320a8cf 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -504,7 +504,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, r = -E2BIG; - if (*nent >= maxnent) + if (WARN_ON(*nent >= maxnent)) goto out; do_host_cpuid(entry, function, 0); @@ -815,6 +815,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, static int do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 func, int *nent, int maxnent, unsigned int type) { + if (*nent >= maxnent) + return -E2BIG; + if (type == KVM_GET_EMULATED_CPUID) return __do_cpuid_func_emulated(entry, func, nent, maxnent);