Fix cg_read_strcmp()

Fix a couple issues with cg_read_strcmp(), to improve correctness of
cgroup tests
- Fix cg_read_strcmp() always returning 0 for empty "needle" strings.
Previously, this function read to a size = 1 buffer when comparing
against empty strings, which would lead to cg_read_strcmp() comparing
two empty strings.
- Fix a memory leak in cg_read_strcmp()

Fixes: 84092dbcf901 ("selftests: cgroup: add memory controller self-tests")
Signed-off-by: Jay Kamat <jgkamat@fb.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>

diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index 1c5d2b2a583b3348b13f47b89c75d5ce504ac621..f857def9a9e6bbd767708b8ec8ef14cc1d6a5c76 100644 (file)
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -89,17 +89,28 @@ int cg_read(const char *cgroup, const char *control, char *buf, size_t len)
 int cg_read_strcmp(const char *cgroup, const char *control,
                   const char *expected)
 {
-       size_t size = strlen(expected) + 1;
+       size_t size;
        char *buf;
+       int ret;
+
+       /* Handle the case of comparing against empty string */
+       if (!expected)
+               size = 32;
+       else
+               size = strlen(expected) + 1;
 
        buf = malloc(size);
        if (!buf)
                return -1;
 
-       if (cg_read(cgroup, control, buf, size))
+       if (cg_read(cgroup, control, buf, size)) {
+               free(buf);
                return -1;
+       }
 
-       return strcmp(expected, buf);
+       ret = strcmp(expected, buf);
+       free(buf);
+       return ret;
 }
 
 int cg_read_strstr(const char *cgroup, const char *control, const char *needle)