[PATCH v3 2/8] libperf cpumap: Ensure empty cpumap is NULL from alloc

[Ian Rogers]

Potential corner cases could cause a cpumap to be allocated with size
0, but an empty cpumap should be represented as NULL. Add a path in
perf_cpu_map__alloc to ensure this.

Suggested-by: James Clark <james.clark at arm.com>
Closes: https://lore.kernel.org/lkml/2cd09e7c-eb88-6726-6169-647dcd0a8101@arm.com/
Signed-off-by: Ian Rogers <irogers at google.com>
---
 tools/lib/perf/cpumap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
index ba49552952c5..cae799ad44e1 100644
--- a/tools/lib/perf/cpumap.c
+++ b/tools/lib/perf/cpumap.c
@@ -18,9 +18,13 @@ void perf_cpu_map__set_nr(struct perf_cpu_map *map, int nr_cpus)
 
 struct perf_cpu_map *perf_cpu_map__alloc(int nr_cpus)
 {
-	RC_STRUCT(perf_cpu_map) *cpus = malloc(sizeof(*cpus) + sizeof(struct perf_cpu) * nr_cpus);
+	RC_STRUCT(perf_cpu_map) *cpus;
 	struct perf_cpu_map *result;
 
+	if (nr_cpus == 0)
+		return NULL;
+
+	cpus = malloc(sizeof(*cpus) + sizeof(struct perf_cpu) * nr_cpus);
 	if (ADD_RC_CHK(result, cpus)) {
 		cpus->nr = nr_cpus;
 		refcount_set(&cpus->refcnt, 1);
-- 
2.43.0.594.gd9cf4e227d-goog