[PATCH 2/2] perf: Fix writing to illegal memory in handling cpumap mask

[zhe.he]

From: He Zhe <zhe.he@xxxxxxxxxxxxx>

cpu_map__snprint_mask would write to illegal memory pointed by zalloc(0)
when there is only one cpu.

This patch fixes the calculation and adds sanity check against the input
parameters.

Signed-off-by: He Zhe <zhe.he@xxxxxxxxxxxxx>
---
 tools/perf/util/cpumap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 3acfbe3..39cce66 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -751,7 +751,10 @@ size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size)
 	unsigned char *bitmap;
 	int last_cpu = cpu_map__cpu(map, map->nr - 1);
 
-	bitmap = zalloc((last_cpu + 7) / 8);
+	if (buf == NULL)
+		return 0;
+
+	bitmap = zalloc(last_cpu / 8 + 1);
 	if (bitmap == NULL) {
 		buf[0] = '\0';
 		return 0;
-- 
2.7.4