[PATCH 4.19 335/338] selftests: cgroup: Test open-time cgroup namespace usage for migration checks

Greg Kroah-Hartman
2022-04-14T14:02:05Z

From: Tejun Heo <tj@kernel.org>

commit bf35a7879f1dfb0d050fe779168bcf25c7de66f5 upstream.

When a task is writing to an fd opened by a different task, the perm check
should use the cgroup namespace of the latter task. Add a test for it.

Tested-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[OP: backport to v4.19: adjust context, add wait.h and fcntl.h includes]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/cgroup/test_core.c | 99 +++++++++++++++++++++++++++++
1 file changed, 99 insertions(+)

--- a/tools/testing/selftests/cgroup/test_core.c
+++ b/tools/testing/selftests/cgroup/test_core.c
@@ -1,8 +1,13 @@
/* SPDX-License-Identifier: GPL-2.0 */

+#define _GNU_SOURCE
#include <linux/limits.h>
+#include <linux/sched.h>
#include <sys/types.h>
+#include <sys/wait.h>
#include <unistd.h>
+#include <fcntl.h>
+#include <sched.h>
#include <stdio.h>
#include <errno.h>

@@ -421,6 +426,99 @@ cleanup:
return ret;
}

+struct lesser_ns_open_thread_arg {
+ const char *path;
+ int fd;
+ int err;
+};
+
+static int lesser_ns_open_thread_fn(void *arg)
+{
+ struct lesser_ns_open_thread_arg *targ = arg;
+
+ targ->fd = open(targ->path, O_RDWR);
+ targ->err = errno;
+ return 0;
+}
+
+/*
+ * cgroup migration permission check should be performed based on the cgroup
+ * namespace at the time of open instead of write.
+ */
+static int test_cgcore_lesser_ns_open(const char *root)
+{
+ static char stack[65536];
+ const uid_t test_euid = 65534; /* usually nobody, any !root is fine */
+ int ret = KSFT_FAIL;
+ char *cg_test_a = NULL, *cg_test_b = NULL;
+ char *cg_test_a_procs = NULL, *cg_test_b_procs = NULL;
+ int cg_test_b_procs_fd = -1;
+ struct lesser_ns_open_thread_arg targ = { .fd = -1 };
+ pid_t pid;
+ int status;
+
+ cg_test_a = cg_name(root, "cg_test_a");
+ cg_test_b = cg_name(root, "cg_test_b");
+
+ if (!cg_test_a || !cg_test_b)
+ goto cleanup;
+
+ cg_test_a_procs = cg_name(cg_test_a, "cgroup.procs");
+ cg_test_b_procs = cg_name(cg_test_b, "cgroup.procs");
+
+ if (!cg_test_a_procs || !cg_test_b_procs)
+ goto cleanup;
+
+ if (cg_create(cg_test_a) || cg_create(cg_test_b))
+ goto cleanup;
+
+ if (cg_enter_current(cg_test_b))
+ goto cleanup;
+
+ if (chown(cg_test_a_procs, test_euid, -1) ||
+ chown(cg_test_b_procs, test_euid, -1))
+ goto cleanup;
+
+ targ.path = cg_test_b_procs;
+ pid = clone(lesser_ns_open_thread_fn, stack + sizeof(stack),
+ CLONE_NEWCGROUP | CLONE_FILES | CLONE_VM | SIGCHLD,
+ &targ);
+ if (pid < 0)
+ goto cleanup;
+
+ if (waitpid(pid, &status, 0) < 0)
+ goto cleanup;
+
+ if (!WIFEXITED(status))
+ goto cleanup;
+
+ cg_test_b_procs_fd = targ.fd;
+ if (cg_test_b_procs_fd < 0)
+ goto cleanup;
+
+ if (cg_enter_current(cg_test_a))
+ goto cleanup;
+
+ if ((status = write(cg_test_b_procs_fd, "0", 1)) >= 0 || errno != ENOENT)
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ cg_enter_current(root);
+ if (cg_test_b_procs_fd >= 0)
+ close(cg_test_b_procs_fd);
+ if (cg_test_b)
+ cg_destroy(cg_test_b);
+ if (cg_test_a)
+ cg_destroy(cg_test_a);
+ free(cg_test_b_procs);
+ free(cg_test_a_procs);
+ free(cg_test_b);
+ free(cg_test_a);
+ return ret;
+}
+
#define T(x) { x, #x }
struct corecg_test {
int (*fn)(const char *root);
@@ -434,6 +532,7 @@ struct corecg_test {
T(test_cgcore_invalid_domain),
T(test_cgcore_populated),
T(test_cgcore_lesser_euid_open),
+ T(test_cgcore_lesser_ns_open),
};
#undef T