syscalls: add selftest for execveat(2)

TARGETS += sysctl

TARGETS += firmware

TARGETS += ftrace

TARGETS += exec

TARGETS_HOTPLUG = cpu-hotplug

TARGETS_HOTPLUG += memory-hotplug

subdir*

script*

execveat

execveat.symlink

execveat.moved

execveat.path.ephemeral

execveat.ephemeral

execveat.denatured

xxxxxxxx*

 No newline at end of file

CC = $(CROSS_COMPILE)gcc

CFLAGS = -Wall

BINARIES = execveat

DEPS = execveat.symlink execveat.denatured script subdir

all: $(BINARIES) $(DEPS)

subdir:

	mkdir -p $@

script:

	echo '#!/bin/sh' > $@

	echo 'exit $$*' >> $@

	chmod +x $@

execveat.symlink: execveat

	ln -s -f $< $@

execveat.denatured: execveat

	cp $< $@

	chmod -x $@

%: %.c

	$(CC) $(CFLAGS) -o $@ $^

run_tests: all

	./execveat

clean:

	rm -rf $(BINARIES) $(DEPS) subdir.moved execveat.moved xxxxx*

/*

 * Copyright (c) 2014 Google, Inc.

 *

 * Licensed under the terms of the GNU GPL License version 2

 *

 * Selftests for execveat(2).

 */

#define _GNU_SOURCE  /* to get O_PATH, AT_EMPTY_PATH */

#include <sys/sendfile.h>

#include <sys/stat.h>

#include <sys/syscall.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <errno.h>

#include <fcntl.h>

#include <limits.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

static char longpath[2 * PATH_MAX] = "";

static char *envp[] = { "IN_TEST=yes", NULL, NULL };

static char *argv[] = { "execveat", "99", NULL };

static int execveat_(int fd, const char *path, char **argv, char **envp,

		     int flags)

{

#ifdef __NR_execveat

	return syscall(__NR_execveat, fd, path, argv, envp, flags);

#else

	errno = -ENOSYS;

	return -1;

#endif

}

#define check_execveat_fail(fd, path, flags, errno)	\

	_check_execveat_fail(fd, path, flags, errno, #errno)

static int _check_execveat_fail(int fd, const char *path, int flags,

				int expected_errno, const char *errno_str)

{

	int rc;

	errno = 0;

	printf("Check failure of execveat(%d, '%s', %d) with %s... ",

		fd, path?:"(null)", flags, errno_str);

	rc = execveat_(fd, path, argv, envp, flags);

	if (rc > 0) {

		printf("[FAIL] (unexpected success from execveat(2))\n");

		return 1;

	}

	if (errno != expected_errno) {

		printf("[FAIL] (expected errno %d (%s) not %d (%s)\n",

			expected_errno, strerror(expected_errno),

			errno, strerror(errno));

		return 1;

	}

	printf("[OK]\n");

	return 0;

}

static int check_execveat_invoked_rc(int fd, const char *path, int flags,

				     int expected_rc)

{

	int status;

	int rc;

	pid_t child;

	int pathlen = path ? strlen(path) : 0;

	if (pathlen > 40)

		printf("Check success of execveat(%d, '%.20s...%s', %d)... ",

			fd, path, (path + pathlen - 20), flags);

	else

		printf("Check success of execveat(%d, '%s', %d)... ",

			fd, path?:"(null)", flags);

	child = fork();

	if (child < 0) {

		printf("[FAIL] (fork() failed)\n");

		return 1;

	}

	if (child == 0) {

		/* Child: do execveat(). */

		rc = execveat_(fd, path, argv, envp, flags);

		printf("[FAIL]: execveat() failed, rc=%d errno=%d (%s)\n",

			rc, errno, strerror(errno));

		exit(1);  /* should not reach here */

	}

	/* Parent: wait for & check child's exit status. */

	rc = waitpid(child, &status, 0);

	if (rc != child) {

		printf("[FAIL] (waitpid(%d,...) returned %d)\n", child, rc);

		return 1;

	}

	if (!WIFEXITED(status)) {

		printf("[FAIL] (child %d did not exit cleanly, status=%08x)\n",

			child, status);

		return 1;

	}

	if (WEXITSTATUS(status) != expected_rc) {

		printf("[FAIL] (child %d exited with %d not %d)\n",

			child, WEXITSTATUS(status), expected_rc);

		return 1;

	}

	printf("[OK]\n");

	return 0;

}

static int check_execveat(int fd, const char *path, int flags)

{

	return check_execveat_invoked_rc(fd, path, flags, 99);

}

static char *concat(const char *left, const char *right)

{

	char *result = malloc(strlen(left) + strlen(right) + 1);

	strcpy(result, left);

	strcat(result, right);

	return result;

}

static int open_or_die(const char *filename, int flags)

{

	int fd = open(filename, flags);

	if (fd < 0) {

		printf("Failed to open '%s'; "

			"check prerequisites are available\n", filename);

		exit(1);

	}

	return fd;

}

static void exe_cp(const char *src, const char *dest)

{

	int in_fd = open_or_die(src, O_RDONLY);

	int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);

	struct stat info;

	fstat(in_fd, &info);

	sendfile(out_fd, in_fd, NULL, info.st_size);

	close(in_fd);

	close(out_fd);

}

#define XX_DIR_LEN 200

static int check_execveat_pathmax(int dot_dfd, const char *src, int is_script)

{

	int fail = 0;

	int ii, count, len;

	char longname[XX_DIR_LEN + 1];

	int fd;

	if (*longpath == '\0') {

		/* Create a filename close to PATH_MAX in length */

		memset(longname, 'x', XX_DIR_LEN - 1);

		longname[XX_DIR_LEN - 1] = '/';

		longname[XX_DIR_LEN] = '\0';

		count = (PATH_MAX - 3) / XX_DIR_LEN;

		for (ii = 0; ii < count; ii++) {

			strcat(longpath, longname);

			mkdir(longpath, 0755);

		}

		len = (PATH_MAX - 3) - (count * XX_DIR_LEN);

		if (len <= 0)

			len = 1;

		memset(longname, 'y', len);

		longname[len] = '\0';

		strcat(longpath, longname);

	}

	exe_cp(src, longpath);

	/*

	 * Execute as a pre-opened file descriptor, which works whether this is

	 * a script or not (because the interpreter sees a filename like

	 * "/dev/fd/20").

	 */

	fd = open(longpath, O_RDONLY);

	if (fd > 0) {

		printf("Invoke copy of '%s' via filename of length %lu:\n",

			src, strlen(longpath));

		fail += check_execveat(fd, "", AT_EMPTY_PATH);

	} else {

		printf("Failed to open length %lu filename, errno=%d (%s)\n",

			strlen(longpath), errno, strerror(errno));

		fail++;

	}

	/*

	 * Execute as a long pathname relative to ".".  If this is a script,

	 * the interpreter will launch but fail to open the script because its

	 * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.

	 */

	if (is_script)

		fail += check_execveat_invoked_rc(dot_dfd, longpath, 0, 127);

	else

		fail += check_execveat(dot_dfd, longpath, 0);

	return fail;

}

static int run_tests(void)

{

	int fail = 0;

	char *fullname = realpath("execveat", NULL);

	char *fullname_script = realpath("script", NULL);

	char *fullname_symlink = concat(fullname, ".symlink");

	int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);

	int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",

					       O_DIRECTORY|O_RDONLY);

	int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);

	int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);

	int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);

	int fd = open_or_die("execveat", O_RDONLY);

	int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);

	int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);

	int fd_denatured = open_or_die("execveat.denatured", O_RDONLY);

	int fd_denatured_path = open_or_die("execveat.denatured",

					    O_RDONLY|O_PATH);

	int fd_script = open_or_die("script", O_RDONLY);

	int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);

	int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",

					    O_RDONLY|O_PATH);

	int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);

	int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);

	int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);

	/* Change file position to confirm it doesn't affect anything */

	lseek(fd, 10, SEEK_SET);

	/* Normal executable file: */

	/*   dfd + path */

	fail += check_execveat(subdir_dfd, "../execveat", 0);

	fail += check_execveat(dot_dfd, "execveat", 0);

	fail += check_execveat(dot_dfd_path, "execveat", 0);

	/*   absolute path */

	fail += check_execveat(AT_FDCWD, fullname, 0);

	/*   absolute path with nonsense dfd */

	fail += check_execveat(99, fullname, 0);

	/*   fd + no path */

	fail += check_execveat(fd, "", AT_EMPTY_PATH);

	/*   O_CLOEXEC fd + no path */

	fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);

	/*   O_PATH fd */

	fail += check_execveat(fd_path, "", AT_EMPTY_PATH);

	/* Mess with executable file that's already open: */

	/*   fd + no path to a file that's been renamed */

	rename("execveat.ephemeral", "execveat.moved");

	fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);

	/*   fd + no path to a file that's been deleted */

	unlink("execveat.moved"); /* remove the file now fd open */

	fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);

	/* Mess with executable file that's already open with O_PATH */

	/*   fd + no path to a file that's been deleted */

	unlink("execveat.path.ephemeral");

	fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);

	/* Invalid argument failures */

	fail += check_execveat_fail(fd, "", 0, ENOENT);

	fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);

	/* Symlink to executable file: */

	/*   dfd + path */

	fail += check_execveat(dot_dfd, "execveat.symlink", 0);

	fail += check_execveat(dot_dfd_path, "execveat.symlink", 0);

	/*   absolute path */

	fail += check_execveat(AT_FDCWD, fullname_symlink, 0);

	/*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */

	fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH);

	fail += check_execveat(fd_symlink, "",

			       AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);

	/* Symlink fails when AT_SYMLINK_NOFOLLOW set: */

	/*   dfd + path */

	fail += check_execveat_fail(dot_dfd, "execveat.symlink",

				    AT_SYMLINK_NOFOLLOW, ELOOP);

	fail += check_execveat_fail(dot_dfd_path, "execveat.symlink",

				    AT_SYMLINK_NOFOLLOW, ELOOP);

	/*   absolute path */

	fail += check_execveat_fail(AT_FDCWD, fullname_symlink,

				    AT_SYMLINK_NOFOLLOW, ELOOP);

	/* Shell script wrapping executable file: */

	/*   dfd + path */

	fail += check_execveat(subdir_dfd, "../script", 0);

	fail += check_execveat(dot_dfd, "script", 0);

	fail += check_execveat(dot_dfd_path, "script", 0);

	/*   absolute path */

	fail += check_execveat(AT_FDCWD, fullname_script, 0);

	/*   fd + no path */

	fail += check_execveat(fd_script, "", AT_EMPTY_PATH);

	fail += check_execveat(fd_script, "",

			       AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);

	/*   O_CLOEXEC fd fails for a script (as script file inaccessible) */

	fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,

				    ENOENT);

	fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);

	/* Mess with script file that's already open: */

	/*   fd + no path to a file that's been renamed */

	rename("script.ephemeral", "script.moved");

	fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);

	/*   fd + no path to a file that's been deleted */

	unlink("script.moved"); /* remove the file while fd open */

	fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);

	/* Rename a subdirectory in the path: */

	rename("subdir.ephemeral", "subdir.moved");

	fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);

	fail += check_execveat(subdir_dfd_ephemeral, "script", 0);

	/* Remove the subdir and its contents */

	unlink("subdir.moved/script");

	unlink("subdir.moved");

	/* Shell loads via deleted subdir OK because name starts with .. */

	fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);

	fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);

	/* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */

	fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);

	/* Invalid path => ENOENT */

	fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);

	fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);

	fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);

	/* Attempt to execute directory => EACCES */

	fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);

	/* Attempt to execute non-executable => EACCES */

	fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);

	fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);

	fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,

				    EACCES);

	/* Attempt to execute nonsense FD => EBADF */

	fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF);

	fail += check_execveat_fail(99, "execveat", 0, EBADF);

	/* Attempt to execute relative to non-directory => ENOTDIR */

	fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR);

	fail += check_execveat_pathmax(dot_dfd, "execveat", 0);

	fail += check_execveat_pathmax(dot_dfd, "script", 1);

	return fail;

}

static void prerequisites(void)

{

	int fd;

	const char *script = "#!/bin/sh\nexit $*\n";

	/* Create ephemeral copies of files */

	exe_cp("execveat", "execveat.ephemeral");

	exe_cp("execveat", "execveat.path.ephemeral");

	exe_cp("script", "script.ephemeral");

	mkdir("subdir.ephemeral", 0755);

	fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);

	write(fd, script, strlen(script));

	close(fd);

}

int main(int argc, char **argv)

{

	int ii;

	int rc;

	const char *verbose = getenv("VERBOSE");

	if (argc >= 2) {

		/* If we are invoked with an argument, don't run tests. */

		const char *in_test = getenv("IN_TEST");

		if (verbose) {

			printf("  invoked with:");

			for (ii = 0; ii < argc; ii++)

				printf(" [%d]='%s'", ii, argv[ii]);

			printf("\n");

		}

		/* Check expected environment transferred. */

		if (!in_test || strcmp(in_test, "yes") != 0) {

			printf("[FAIL] (no IN_TEST=yes in env)\n");

			return 1;

		}

		/* Use the final argument as an exit code. */

		rc = atoi(argv[argc - 1]);

		fflush(stdout);

	} else {

		prerequisites();

		if (verbose)

			envp[1] = "VERBOSE=1";

		rc = run_tests();

		if (rc > 0)

			printf("%d tests failed\n", rc);

	}

	return rc;

}