--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/limits.h>
+#include <signal.h>
+
+#include "../kselftest.h"
+#include "cgroup_util.h"
+
+static int idle_process_fn(const char *cgroup, void *arg)
+{
+ (void)pause();
+ return 0;
+}
+
+static int do_migration_fn(const char *cgroup, void *arg)
+{
+ int object_pid = (int)(size_t)arg;
+
+ if (setuid(TEST_UID))
+ return EXIT_FAILURE;
+
+ // XXX checking /proc/$pid/cgroup would be quicker than wait
+ if (cg_enter(cgroup, object_pid) ||
+ cg_wait_for_proc_count(cgroup, 1))
+ return EXIT_FAILURE;
+
+ return EXIT_SUCCESS;
+}
+
+static int do_controller_fn(const char *cgroup, void *arg)
+{
+ const char *child = cgroup;
+ const char *parent = arg;
+
+ if (setuid(TEST_UID))
+ return EXIT_FAILURE;
+
+ if (!cg_read_strstr(child, "cgroup.controllers", "cpuset"))
+ return EXIT_FAILURE;
+
+ if (cg_write(parent, "cgroup.subtree_control", "+cpuset"))
+ return EXIT_FAILURE;
+
+ if (cg_read_strstr(child, "cgroup.controllers", "cpuset"))
+ return EXIT_FAILURE;
+
+ if (cg_write(parent, "cgroup.subtree_control", "-cpuset"))
+ return EXIT_FAILURE;
+
+ if (!cg_read_strstr(child, "cgroup.controllers", "cpuset"))
+ return EXIT_FAILURE;
+
+ return EXIT_SUCCESS;
+}
+
+/*
+ * Migrate a process between two sibling cgroups.
+ * The success should only depend on the parent cgroup permissions and not the
+ * migrated process itself (cpuset controller is in place because it uses
+ * security_task_setscheduler() in cgroup v1).
+ *
+ * Deliberately don't set cpuset.cpus in children to avoid definining migration
+ * permissions between two different cpusets.
+ */
+static int test_cpuset_perms_object(const char *root, bool allow)
+{
+ char *parent = NULL, *child_src = NULL, *child_dst = NULL;
+ char *parent_procs = NULL, *child_src_procs = NULL, *child_dst_procs = NULL;
+ const uid_t test_euid = TEST_UID;
+ int object_pid = 0;
+ int ret = KSFT_FAIL;
+
+ parent = cg_name(root, "cpuset_test_0");
+ if (!parent)
+ goto cleanup;
+ parent_procs = cg_name(parent, "cgroup.procs");
+ if (!parent_procs)
+ goto cleanup;
+ if (cg_create(parent))
+ goto cleanup;
+
+ child_src = cg_name(parent, "cpuset_test_1");
+ if (!child_src)
+ goto cleanup;
+ child_src_procs = cg_name(child_src, "cgroup.procs");
+ if (!child_src_procs)
+ goto cleanup;
+ if (cg_create(child_src))
+ goto cleanup;
+
+ child_dst = cg_name(parent, "cpuset_test_2");
+ if (!child_dst)
+ goto cleanup;
+ child_dst_procs = cg_name(child_dst, "cgroup.procs");
+ if (!child_dst_procs)
+ goto cleanup;
+ if (cg_create(child_dst))
+ goto cleanup;
+
+ if (cg_write(parent, "cgroup.subtree_control", "+cpuset"))
+ goto cleanup;
+
+ if (cg_read_strstr(child_src, "cgroup.controllers", "cpuset") ||
+ cg_read_strstr(child_dst, "cgroup.controllers", "cpuset"))
+ goto cleanup;
+
+ /* Enable permissions along src->dst tree path */
+ if (chown(child_src_procs, test_euid, -1) ||
+ chown(child_dst_procs, test_euid, -1))
+ goto cleanup;
+
+ if (allow && chown(parent_procs, test_euid, -1))
+ goto cleanup;
+
+ /* Fork a privileged child as a test object */
+ object_pid = cg_run_nowait(child_src, idle_process_fn, NULL);
+ if (object_pid < 0)
+ goto cleanup;
+
+ /* Carry out migration in a child process that can drop all privileges
+ * (including capabilities), the main process must remain privileged for
+ * cleanup.
+ * Child process's cgroup is irrelevant but we place it into child_dst
+ * as hacky way to pass information about migration target to the child.
+ */
+ if (allow ^ (cg_run(child_dst, do_migration_fn, (void *)(size_t)object_pid) == EXIT_SUCCESS))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (object_pid > 0) {
+ (void)kill(object_pid, SIGTERM);
+ (void)clone_reap(object_pid, WEXITED);
+ }
+
+ cg_destroy(child_dst);
+ free(child_dst_procs);
+ free(child_dst);
+
+ cg_destroy(child_src);
+ free(child_src_procs);
+ free(child_src);
+
+ cg_destroy(parent);
+ free(parent_procs);
+ free(parent);
+
+ return ret;
+}
+
+static int test_cpuset_perms_object_allow(const char *root)
+{
+ return test_cpuset_perms_object(root, true);
+}
+
+static int test_cpuset_perms_object_deny(const char *root)
+{
+ return test_cpuset_perms_object(root, false);
+}
+
+/*
+ * Migrate a process between parent and child implicitely
+ * Implicit migration happens when a controller is enabled/disabled.
+ *
+ */
+static int test_cpuset_perms_subtree(const char *root)
+{
+ char *parent = NULL, *child = NULL;
+ char *parent_procs = NULL, *parent_subctl = NULL, *child_procs = NULL;
+ const uid_t test_euid = TEST_UID;
+ int object_pid = 0;
+ int ret = KSFT_FAIL;
+
+ 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;
+ if (cg_create(parent))
+ goto cleanup;
+
+ 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))
+ goto cleanup;
+
+ /* Put a privileged child in the subtree and modify controller state
+ * from an unprivileged process, the main process remains privileged
+ * for cleanup.
+ * The unprivileged child runs in subtree too to avoid parent and
+ * internal-node constraing violation.
+ */
+ object_pid = cg_run_nowait(child, idle_process_fn, NULL);
+ if (object_pid < 0)
+ goto cleanup;
+
+ if (cg_run(child, do_controller_fn, parent) != EXIT_SUCCESS)
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (object_pid > 0) {
+ (void)kill(object_pid, SIGTERM);
+ (void)clone_reap(object_pid, WEXITED);
+ }
+
+ cg_destroy(child);
+ free(child_procs);
+ free(child);
+
+ cg_destroy(parent);
+ free(parent_subctl);
+ free(parent_procs);
+ free(parent);
+
+ return ret;
+}
+
+
+#define T(x) { x, #x }
+struct cpuset_test {
+ int (*fn)(const char *root);
+ const char *name;
+} tests[] = {
+ T(test_cpuset_perms_object_allow),
+ T(test_cpuset_perms_object_deny),
+ T(test_cpuset_perms_subtree),
+};
+#undef T
+
+int main(int argc, char *argv[])
+{
+ char root[PATH_MAX];
+ int i, ret = EXIT_SUCCESS;
+
+ if (cg_find_unified_root(root, sizeof(root)))
+ ksft_exit_skip("cgroup v2 isn't mounted\n");
+
+ if (cg_read_strstr(root, "cgroup.subtree_control", "cpuset"))
+ if (cg_write(root, "cgroup.subtree_control", "+cpuset"))
+ ksft_exit_skip("Failed to set cpuset controller\n");
+
+ for (i = 0; i < ARRAY_SIZE(tests); i++) {
+ switch (tests[i].fn(root)) {
+ case KSFT_PASS:
+ ksft_test_result_pass("%s\n", tests[i].name);
+ break;
+ case KSFT_SKIP:
+ ksft_test_result_skip("%s\n", tests[i].name);
+ break;
+ default:
+ ret = EXIT_FAILURE;
+ ksft_test_result_fail("%s\n", tests[i].name);
+ break;
+ }
+ }
+
+ return ret;
+}
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