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>
---
 tools/testing/selftests/cgroup/lib/cgroup_util.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/cgroup/lib/cgroup_util.c b/tools/testing/selftests/cgroup/lib/cgroup_util.c
index 6a7295347e90..0c5e6d4bbc3a 100644
--- 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;
 }
-- 
2.25.1

On Mon, May 11, 2026 at 02:08:53PM +0800, Hongfu Li wrote:
> 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>
> ---

Reviewed-by: Vishal Moola <vishal.moola@gmail.com>

Hello,

Applied to cgroup/for-7.2.

Thanks.

--
tejun