[PATCH] selftests: cgroup: simplify cpuset subtree permissions test

Simplify test_cpuset_perms_subtree by removing unnecessary chown of
cgroup.procs files. The test verifies implicit migration triggered by
enabling/disabling the cpuset controller via cgroup.subtree_control.

Implicit migration is handled internally by the kernel through
cgroup_update_dfl_csses() when subtree_control is modified, and does
not require cgroup.procs write permission. Only cgroup.subtree_control
permission is needed to trigger the controller state change.

Remove the allocation and cleanup of parent_procs and child_procs
variables that are no longer needed.

Signed-off-by: Shaojie Sun <[email protected]>
---
 tools/testing/selftests/cgroup/test_cpuset.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_cpuset.c b/tools/testing/selftests/cgroup/test_cpuset.c
index c5cf8b56ceb8..b323addcc519 100644
--- a/tools/testing/selftests/cgroup/test_cpuset.c
+++ b/tools/testing/selftests/cgroup/test_cpuset.c
@@ -167,7 +167,7 @@ static int test_cpuset_perms_object_deny(const char *root)
 static int test_cpuset_perms_subtree(const char *root)
 {
 	char *parent = NULL, *child = NULL;
-	char *parent_procs = NULL, *parent_subctl = NULL, *child_procs = NULL;
+	char *parent_subctl = NULL;
 	const uid_t test_euid = TEST_UID;
 	int object_pid = 0;
 	int ret = KSFT_FAIL;
@@ -175,9 +175,6 @@ static int test_cpuset_perms_subtree(const char *root)
 	parent = cg_name(root, "cpuset_test_0");
 	if (!parent)
 		goto cleanup;
-	parent_procs = cg_name(parent, "cgroup.procs");
-	if (!parent_procs)
-		goto cleanup;
 	parent_subctl = cg_name(parent, "cgroup.subtree_control");
 	if (!parent_subctl)
 		goto cleanup;
@@ -187,16 +184,11 @@ static int test_cpuset_perms_subtree(const char *root)
 	child = cg_name(parent, "cpuset_test_1");
 	if (!child)
 		goto cleanup;
-	child_procs = cg_name(child, "cgroup.procs");
-	if (!child_procs)
-		goto cleanup;
 	if (cg_create(child))
 		goto cleanup;
 
-	/* Enable permissions as in a delegated subtree */
-	if (chown(parent_procs, test_euid, -1) ||
-	    chown(parent_subctl, test_euid, -1) ||
-	    chown(child_procs, test_euid, -1))
+	/* Grant minimal subtree_control permission to trigger implicit migration */
+	if (chown(parent_subctl, test_euid, -1))
 		goto cleanup;
 
 	/* Put a privileged child in the subtree and modify controller state
@@ -221,12 +213,10 @@ static int test_cpuset_perms_subtree(const char *root)
 	}
 
 	cg_destroy(child);
-	free(child_procs);
 	free(child);
 
 	cg_destroy(parent);
 	free(parent_subctl);
-	free(parent_procs);
 	free(parent);
 
 	return ret;
-- 
2.50.1