linux/tools/testing/selftests/fchmodat2/fchmodat2_test.c

// SPDX-License-Identifier: GPL-2.0-or-later

#define _GNU_SOURCE
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <syscall.h>
#include <unistd.h>

#include "kselftest.h"

struct testdir {
	char *dirname;
	int dfd;
};

int sys_fchmodat2(int dfd, const char *filename, mode_t mode, int flags)
{
	int ret = syscall(__NR_fchmodat2, dfd, filename, mode, flags);

	return ret >= 0 ? ret : -errno;
}

static void setup_testdir(struct testdir *testdir)
{
	int ret, dfd;
	char dirname[] = "/tmp/ksft-fchmodat2.XXXXXX";

	/* Make the top-level directory. */
	if (!mkdtemp(dirname))
		ksft_exit_fail_msg("%s: failed to create tmpdir\n", __func__);

	dfd = open(dirname, O_PATH | O_DIRECTORY);
	if (dfd < 0) {
		ksft_perror("failed to open tmpdir");
		goto err;
	}

	ret = openat(dfd, "regfile", O_CREAT | O_WRONLY | O_TRUNC, 0644);
	if (ret < 0) {
		ksft_perror("failed to create file in tmpdir");
		goto err;
	}
	close(ret);

	ret = symlinkat("regfile", dfd, "symlink");
	if (ret < 0) {
		ksft_perror("symlinkat() failed");
		goto err_regfile;
	}

	testdir->dirname = strdup(dirname);
	if (!testdir->dirname) {
		ksft_perror("Out of memory");
		goto err_symlink;
	}
	testdir->dfd = dfd;

	return;

err_symlink:
	unlinkat(testdir->dfd, "symlink", 0);
err_regfile:
	unlinkat(testdir->dfd, "regfile", 0);
err:
	unlink(dirname);
	ksft_exit_fail();
}

static void cleanup_testdir(struct testdir *testdir)
{
	unlinkat(testdir->dfd, "regfile", 0);
	unlinkat(testdir->dfd, "symlink", 0);
	rmdir(testdir->dirname);
	free(testdir->dirname);
}

int expect_mode(int dfd, const char *filename, mode_t expect_mode)
{
	struct stat st;
	int ret = fstatat(dfd, filename, &st, AT_SYMLINK_NOFOLLOW);

	if (ret) {
		ksft_perror("fstatat() failed\n");
		return 0;
	}

	return (st.st_mode == expect_mode);
}

void test_regfile(void)
{
	struct testdir testdir;
	int ret;

	setup_testdir(&testdir);

	ret = sys_fchmodat2(testdir.dfd, "regfile", 0640, 0);

	if (ret < 0) {
		ksft_perror("fchmodat2(noflag) failed");
		goto out;
	}

	if (!expect_mode(testdir.dfd, "regfile", 0100640)) {
		ksft_print_msg("%s: wrong file mode bits after fchmodat2\n",
				__func__);
		ret = 1;
		goto out;
	}

	ret = sys_fchmodat2(testdir.dfd, "regfile", 0600, AT_SYMLINK_NOFOLLOW);

	if (ret < 0) {
		ksft_perror("fchmodat2(AT_SYMLINK_NOFOLLOW) failed");
		goto out;
	}

	if (!expect_mode(testdir.dfd, "regfile", 0100600)) {
		ksft_print_msg("%s: wrong file mode bits after fchmodat2 with nofollow\n",
			       __func__);
		ret = 1;
	}

out:
	ksft_test_result(ret == 0, "fchmodat2(regfile)\n");
	cleanup_testdir(&testdir);
}

void test_symlink(void)
{
	struct testdir testdir;
	int ret;

	setup_testdir(&testdir);

	ret = sys_fchmodat2(testdir.dfd, "symlink", 0640, 0);

	if (ret < 0) {
		ksft_perror("fchmodat2(noflag) failed");
		goto err;
	}

	if (!expect_mode(testdir.dfd, "regfile", 0100640)) {
		ksft_print_msg("%s: wrong file mode bits after fchmodat2\n",
			       __func__);
		goto err;
	}

	if (!expect_mode(testdir.dfd, "symlink", 0120777)) {
		ksft_print_msg("%s: wrong symlink mode bits after fchmodat2\n",
			       __func__);
		goto err;
	}

	ret = sys_fchmodat2(testdir.dfd, "symlink", 0600, AT_SYMLINK_NOFOLLOW);

	/*
	 * On certain filesystems (xfs or btrfs), chmod operation fails. So we
	 * first check the symlink target but if the operation fails we mark the
	 * test as skipped.
	 *
	 * https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00467.html
	 */
	if (ret == 0 && !expect_mode(testdir.dfd, "symlink", 0120600)) {
		ksft_print_msg("%s: wrong symlink mode bits after fchmodat2 with nofollow\n",
				__func__);
		ret = 1;
		goto err;
	}

	if (!expect_mode(testdir.dfd, "regfile", 0100640)) {
		ksft_print_msg("%s: wrong file mode bits after fchmodat2 with nofollow\n",
			       __func__);
	}

	if (ret != 0)
		ksft_test_result_skip("fchmodat2(symlink)\n");
	else
		ksft_test_result_pass("fchmodat2(symlink)\n");
	cleanup_testdir(&testdir);
	return;

err:
	ksft_test_result_fail("fchmodat2(symlink)\n");
	cleanup_testdir(&testdir);
}

#define NUM_TESTS 2

int main(int argc, char **argv)
{
	ksft_print_header();
	ksft_set_plan(NUM_TESTS);

	test_regfile();
	test_symlink();

	ksft_finished();
}