selftests/cgroup: Add NULL check after malloc in cgroup_util.c

Add NULL checks after malloc() in three helper functions to prevent
NULL pointer dereference on memory allocation failure.
- cg_name()
- cg_name_indexed()
- cg_control()

These functions allocate memory with malloc() but previously called
snprintf() unconditionally, which would trigger undefined behavior
if allocation fails.

Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/tools/testing/selftests/cgroup/lib/cgroup_util.c b/tools/testing/selftests/cgroup/lib/cgroup_util.c
index 6a7295347e90b1cc1298aa80aa01a8dbfa21e936..0c5e6d4bbc3ac4997722a786d236ad5e648e0df6 100644 (file)
--- a/tools/testing/selftests/cgroup/lib/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/lib/cgroup_util.c
@@ -59,7 +59,8 @@ char *cg_name(const char *root, const char *name)
        size_t len = strlen(root) + strlen(name) + 2;
        char *ret = malloc(len);
 
-       snprintf(ret, len, "%s/%s", root, name);
+       if (ret)
+               snprintf(ret, len, "%s/%s", root, name);
 
        return ret;
 }
@@ -69,7 +70,8 @@ char *cg_name_indexed(const char *root, const char *name, int index)
        size_t len = strlen(root) + strlen(name) + 10;
        char *ret = malloc(len);
 
-       snprintf(ret, len, "%s/%s_%d", root, name, index);
+       if (ret)
+               snprintf(ret, len, "%s/%s_%d", root, name, index);
 
        return ret;
 }
@@ -79,7 +81,8 @@ char *cg_control(const char *cgroup, const char *control)
        size_t len = strlen(cgroup) + strlen(control) + 2;
        char *ret = malloc(len);
 
-       snprintf(ret, len, "%s/%s", cgroup, control);
+       if (ret)
+               snprintf(ret, len, "%s/%s", cgroup, control);
 
        return ret;
 }