selftests: add a test for the foreign mnt ns extensions

This tests both statmount and listmount to make sure they work with the
extensions that allow us to specify a mount ns to enter in order to find
the mount entries.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/2d1a35bc9ab94b4656c056c420f25e429e7eb0b1.1719243756.git.josef@toxicpanda.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

tools/testing/selftests/filesystems/statmount/statmount_test_ns.c

@@ -0,0 +1,364 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <sched.h>
+#include <stdlib.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <linux/nsfs.h>
+#include <linux/stat.h>
+
+#include "statmount.h"
+#include "../../kselftest.h"
+
+#define NSID_PASS 0
+#define NSID_FAIL 1
+#define NSID_SKIP 2
+#define NSID_ERROR 3
+
+static void handle_result(int ret, const char *testname)
+{
+	if (ret == NSID_PASS)
+		ksft_test_result_pass("%s\n", testname);
+	else if (ret == NSID_FAIL)
+		ksft_test_result_fail("%s\n", testname);
+	else if (ret == NSID_ERROR)
+		ksft_exit_fail_msg("%s\n", testname);
+	else
+		ksft_test_result_skip("%s\n", testname);
+}
+
+static inline int wait_for_pid(pid_t pid)
+{
+	int status, ret;
+
+again:
+	ret = waitpid(pid, &status, 0);
+	if (ret == -1) {
+		if (errno == EINTR)
+			goto again;
+
+		ksft_print_msg("waitpid returned -1, errno=%d\n", errno);
+		return -1;
+	}
+
+	if (!WIFEXITED(status)) {
+		ksft_print_msg(
+		       "waitpid !WIFEXITED, WIFSIGNALED=%d, WTERMSIG=%d\n",
+		       WIFSIGNALED(status), WTERMSIG(status));
+		return -1;
+	}
+
+	ret = WEXITSTATUS(status);
+	return ret;
+}
+
+static int get_mnt_ns_id(const char *mnt_ns, uint64_t *mnt_ns_id)
+{
+	int fd = open(mnt_ns, O_RDONLY);
+
+	if (fd < 0) {
+		ksft_print_msg("failed to open for ns %s: %s\n",
+			       mnt_ns, strerror(errno));
+		sleep(60);
+		return NSID_ERROR;
+	}
+
+	if (ioctl(fd, NS_GET_MNTNS_ID, mnt_ns_id) < 0) {
+		ksft_print_msg("failed to get the nsid for ns %s: %s\n",
+			       mnt_ns, strerror(errno));
+		return NSID_ERROR;
+	}
+	close(fd);
+	return NSID_PASS;
+}
+
+static int get_mnt_id(const char *path, uint64_t *mnt_id)
+{
+	struct statx sx;
+	int ret;
+
+	ret = statx(AT_FDCWD, path, 0, STATX_MNT_ID_UNIQUE, &sx);
+	if (ret == -1) {
+		ksft_print_msg("retrieving unique mount ID for %s: %s\n", path,
+			       strerror(errno));
+		return NSID_ERROR;
+	}
+
+	if (!(sx.stx_mask & STATX_MNT_ID_UNIQUE)) {
+		ksft_print_msg("no unique mount ID available for %s\n", path);
+		return NSID_ERROR;
+	}
+
+	*mnt_id = sx.stx_mnt_id;
+	return NSID_PASS;
+}
+
+static int write_file(const char *path, const char *val)
+{
+	int fd = open(path, O_WRONLY);
+	size_t len = strlen(val);
+	int ret;
+
+	if (fd == -1) {
+		ksft_print_msg("opening %s for write: %s\n", path, strerror(errno));
+		return NSID_ERROR;
+	}
+
+	ret = write(fd, val, len);
+	if (ret == -1) {
+		ksft_print_msg("writing to %s: %s\n", path, strerror(errno));
+		return NSID_ERROR;
+	}
+	if (ret != len) {
+		ksft_print_msg("short write to %s\n", path);
+		return NSID_ERROR;
+	}
+
+	ret = close(fd);
+	if (ret == -1) {
+		ksft_print_msg("closing %s\n", path);
+		return NSID_ERROR;
+	}
+
+	return NSID_PASS;
+}
+
+static int setup_namespace(void)
+{
+	int ret;
+	char buf[32];
+	uid_t uid = getuid();
+	gid_t gid = getgid();
+
+	ret = unshare(CLONE_NEWNS|CLONE_NEWUSER|CLONE_NEWPID);
+	if (ret == -1)
+		ksft_exit_fail_msg("unsharing mountns and userns: %s\n",
+				   strerror(errno));
+
+	sprintf(buf, "0 %d 1", uid);
+	ret = write_file("/proc/self/uid_map", buf);
+	if (ret != NSID_PASS)
+		return ret;
+	ret = write_file("/proc/self/setgroups", "deny");
+	if (ret != NSID_PASS)
+		return ret;
+	sprintf(buf, "0 %d 1", gid);
+	ret = write_file("/proc/self/gid_map", buf);
+	if (ret != NSID_PASS)
+		return ret;
+
+	ret = mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
+	if (ret == -1) {
+		ksft_print_msg("making mount tree private: %s\n",
+			       strerror(errno));
+		return NSID_ERROR;
+	}
+
+	return NSID_PASS;
+}
+
+static int _test_statmount_mnt_ns_id(void)
+{
+	struct statmount sm;
+	uint64_t mnt_ns_id;
+	uint64_t root_id;
+	int ret;
+
+	ret = get_mnt_ns_id("/proc/self/ns/mnt", &mnt_ns_id);
+	if (ret != NSID_PASS)
+		return ret;
+
+	ret = get_mnt_id("/", &root_id);
+	if (ret != NSID_PASS)
+		return ret;
+
+	ret = statmount(root_id, 0, STATMOUNT_MNT_NS_ID, &sm, sizeof(sm), 0);
+	if (ret == -1) {
+		ksft_print_msg("statmount mnt ns id: %s\n", strerror(errno));
+		return NSID_ERROR;
+	}
+
+	if (sm.size != sizeof(sm)) {
+		ksft_print_msg("unexpected size: %u != %u\n", sm.size,
+			       (uint32_t)sizeof(sm));
+		return NSID_FAIL;
+	}
+	if (sm.mask != STATMOUNT_MNT_NS_ID) {
+		ksft_print_msg("statmount mnt ns id unavailable\n");
+		return NSID_SKIP;
+	}
+
+	if (sm.mnt_ns_id != mnt_ns_id) {
+		ksft_print_msg("unexpected mnt ns ID: 0x%llx != 0x%llx\n",
+			       (unsigned long long)sm.mnt_ns_id,
+			       (unsigned long long)mnt_ns_id);
+		return NSID_FAIL;
+	}
+
+	return NSID_PASS;
+}
+
+static void test_statmount_mnt_ns_id(void)
+{
+	pid_t pid;
+	int ret;
+
+	pid = fork();
+	if (pid < 0)
+		ksft_exit_fail_msg("failed to fork: %s\n", strerror(errno));
+
+	/* We're the original pid, wait for the result. */
+	if (pid != 0) {
+		ret = wait_for_pid(pid);
+		handle_result(ret, "test statmount ns id");
+		return;
+	}
+
+	ret = setup_namespace();
+	if (ret != NSID_PASS)
+		exit(ret);
+	ret = _test_statmount_mnt_ns_id();
+	exit(ret);
+}
+
+static int validate_external_listmount(pid_t pid, uint64_t child_nr_mounts)
+{
+	uint64_t list[256];
+	uint64_t mnt_ns_id;
+	uint64_t nr_mounts;
+	char buf[256];
+	int ret;
+
+	/* Get the mount ns id for our child. */
+	snprintf(buf, sizeof(buf), "/proc/%lu/ns/mnt", (unsigned long)pid);
+	ret = get_mnt_ns_id(buf, &mnt_ns_id);
+
+	nr_mounts = listmount(LSMT_ROOT, mnt_ns_id, 0, list, 256, 0);
+	if (nr_mounts == (uint64_t)-1) {
+		ksft_print_msg("listmount: %s\n", strerror(errno));
+		return NSID_ERROR;
+	}
+
+	if (nr_mounts != child_nr_mounts) {
+		ksft_print_msg("listmount results is %zi != %zi\n", nr_mounts,
+			       child_nr_mounts);
+		return NSID_FAIL;
+	}
+
+	/* Validate that all of our entries match our mnt_ns_id. */
+	for (int i = 0; i < nr_mounts; i++) {
+		struct statmount sm;
+
+		ret = statmount(list[i], mnt_ns_id, STATMOUNT_MNT_NS_ID, &sm,
+				sizeof(sm), 0);
+		if (ret < 0) {
+			ksft_print_msg("statmount mnt ns id: %s\n", strerror(errno));
+			return NSID_ERROR;
+		}
+
+		if (sm.mask != STATMOUNT_MNT_NS_ID) {
+			ksft_print_msg("statmount mnt ns id unavailable\n");
+			return NSID_SKIP;
+		}
+
+		if (sm.mnt_ns_id != mnt_ns_id) {
+			ksft_print_msg("listmount gave us the wrong ns id: 0x%llx != 0x%llx\n",
+				       (unsigned long long)sm.mnt_ns_id,
+				       (unsigned long long)mnt_ns_id);
+			return NSID_FAIL;
+		}
+	}
+
+	return NSID_PASS;
+}
+
+static void test_listmount_ns(void)
+{
+	uint64_t nr_mounts;
+	char pval;
+	int child_ready_pipe[2];
+	int parent_ready_pipe[2];
+	pid_t pid;
+	int ret, child_ret;
+
+	if (pipe(child_ready_pipe) < 0)
+		ksft_exit_fail_msg("failed to create the child pipe: %s\n",
+				   strerror(errno));
+	if (pipe(parent_ready_pipe) < 0)
+		ksft_exit_fail_msg("failed to create the parent pipe: %s\n",
+				   strerror(errno));
+
+	pid = fork();
+	if (pid < 0)
+		ksft_exit_fail_msg("failed to fork: %s\n", strerror(errno));
+
+	if (pid == 0) {
+		char cval;
+		uint64_t list[256];
+
+		close(child_ready_pipe[0]);
+		close(parent_ready_pipe[1]);
+
+		ret = setup_namespace();
+		if (ret != NSID_PASS)
+			exit(ret);
+
+		nr_mounts = listmount(LSMT_ROOT, 0, 0, list, 256, 0);
+		if (nr_mounts == (uint64_t)-1) {
+			ksft_print_msg("listmount: %s\n", strerror(errno));
+			exit(NSID_FAIL);
+		}
+
+		/*
+		 * Tell our parent how many mounts we have, and then wait for it
+		 * to tell us we're done.
+		 */
+		write(child_ready_pipe[1], &nr_mounts, sizeof(nr_mounts));
+		read(parent_ready_pipe[0], &cval, sizeof(cval));
+		exit(NSID_PASS);
+	}
+
+	close(child_ready_pipe[1]);
+	close(parent_ready_pipe[0]);
+
+	/* Wait until the child has created everything. */
+	if (read(child_ready_pipe[0], &nr_mounts, sizeof(nr_mounts)) !=
+	    sizeof(nr_mounts))
+		ret = NSID_ERROR;
+
+	ret = validate_external_listmount(pid, nr_mounts);
+
+	if (write(parent_ready_pipe[1], &pval, sizeof(pval)) != sizeof(pval))
+		ret = NSID_ERROR;
+
+	child_ret = wait_for_pid(pid);
+	if (child_ret != NSID_PASS)
+		ret = child_ret;
+	handle_result(ret, "test listmount ns id");
+}
+
+int main(void)
+{
+	int ret;
+
+	ksft_print_header();
+	ret = statmount(0, 0, 0, NULL, 0, 0);
+	assert(ret == -1);
+	if (errno == ENOSYS)
+		ksft_exit_skip("statmount() syscall not supported\n");
+
+	ksft_set_plan(2);
+	test_statmount_mnt_ns_id();
+	test_listmount_ns();
+
+	if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+		ksft_exit_fail();
+	else
+		ksft_exit_pass();
+}