perf kvm: Handle realloc failures

Save previous pointer and free on failure.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1369527896-3650-7-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-kvm.c

@@ -328,6 +328,7 @@ static int kvm_events_hash_fn(u64 key)
 static bool kvm_event_expand(struct kvm_event *event, int vcpu_id)
 {
 	int old_max_vcpu = event->max_vcpu;
+	void *prev;
 
 	if (vcpu_id < event->max_vcpu)
 		return true;
@@ -335,9 +336,11 @@ static bool kvm_event_expand(struct kvm_event *event, int vcpu_id)
 	while (event->max_vcpu <= vcpu_id)
 		event->max_vcpu += DEFAULT_VCPU_NUM;
 
+	prev = event->vcpu;
 	event->vcpu = realloc(event->vcpu,
 			      event->max_vcpu * sizeof(*event->vcpu));
 	if (!event->vcpu) {
+		free(prev);
 		pr_err("Not enough memory\n");
 		return false;
 	}