Revert "KVM: x86: fix out-of-bounds write in KVM_GET_EMULATED_CPUID (CVE-2019-19332)"

BugLink: https://bugs.launchpad.net/bugs/1858489

This reverts commit fa1742ad in favor of
the upstream stable version.
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/kvm/cpuid.c

@@ -375,7 +375,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 
 	r = -E2BIG;
 
-	if (WARN_ON(*nent >= maxnent))
+	if (*nent >= maxnent)
 		goto out;
 
 	do_cpuid_1_ent(entry, function, index);
@@ -670,9 +670,6 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 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);