is_directory() uses sprintf() which could potentially result in a
stack buffer overrun.  Change to use snprintf() and assert that
the output fits in the buffer.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
A better fix would be to pass the directory fd in and use fstatat()
but I don't know whether you want to support older kernel versions
or C libraries that don't support this.

Ben.

 tools/perf/util/path.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/path.c b/tools/perf/util/path.c
index ca56ba2dd3da..333e20f78ced 100644
--- a/tools/perf/util/path.c
+++ b/tools/perf/util/path.c
@@ -84,8 +84,11 @@ bool is_directory(const char *base_path, const struct dirent *dent)
 {
 	char path[PATH_MAX];
 	struct stat st;
+	int len;
+
+	len = snprintf(path, sizeof(path), "%s/%s", base_path, dent->d_name);
+	assert((size_t)len < sizeof(path));
 
-	sprintf(path, "%s/%s", base_path, dent->d_name);
 	if (stat(path, &st))
 		return false;