Commit ce290a19 authored by Christian Brauner's avatar Christian Brauner Committed by Greg Kroah-Hartman
Browse files

selftests: add devpts selftests 



This adds tests to check:
- bind-mounts from /dev/pts/ptmx to /dev/ptmx work
- non-standard mounts of devpts work
- bind-mounts of /dev/pts/ptmx to locations that do not resolve to a valid
  slave pty path under the originating devpts mount fail

Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4e15f760

tools/testing/selftests/Makefile

+1 −0
Original line number Original line Diff line number Diff line
@@ -7,6 +7,7 @@ TARGETS += cpufreq 
TARGETS += cpu-hotplug

TARGETS += cpu-hotplug

TARGETS += efivarfs

TARGETS += efivarfs

TARGETS += exec

TARGETS += exec

TARGETS += filesystems

TARGETS += firmware

TARGETS += firmware

TARGETS += ftrace

TARGETS += ftrace

TARGETS += futex

TARGETS += futex

tools/testing/selftests/filesystems/.gitignore

+1 −0
Original line number Original line Diff line number Diff line 
dnotify_test

dnotify_test

devpts_pts

tools/testing/selftests/filesystems/Makefile

+1 −1
Original line number Original line Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

# SPDX-License-Identifier: GPL-2.0

TEST_PROGS := dnotify_test

TEST_PROGS := dnotify_test devpts_pts

all: $(TEST_PROGS)

all: $(TEST_PROGS)





include ../lib.mk

include ../lib.mk

tools/testing/selftests/filesystems/devpts_pts.c

0 → 100644
+313 −0
Original line number Original line Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE

#include <errno.h>

#include <fcntl.h>

#include <sched.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <sys/ioctl.h>

#include <sys/mount.h>

#include <sys/wait.h>



static bool terminal_dup2(int duplicate, int original)

{

	int ret;



	ret = dup2(duplicate, original);

	if (ret < 0)

		return false;



	return true;

}



static int terminal_set_stdfds(int fd)

{

	int i;



	if (fd < 0)

		return 0;



	for (i = 0; i < 3; i++)

		if (!terminal_dup2(fd, (int[]){STDIN_FILENO, STDOUT_FILENO,

					       STDERR_FILENO}[i]))

			return -1;



	return 0;

}



static int login_pty(int fd)

{

	int ret;



	setsid();



	ret = ioctl(fd, TIOCSCTTY, NULL);

	if (ret < 0)

		return -1;



	ret = terminal_set_stdfds(fd);

	if (ret < 0)

		return -1;



	if (fd > STDERR_FILENO)

		close(fd);



	return 0;

}



static int wait_for_pid(pid_t pid)

{

	int status, ret;



again:

	ret = waitpid(pid, &status, 0);

	if (ret == -1) {

		if (errno == EINTR)

			goto again;

		return -1;

	}

	if (ret != pid)

		goto again;



	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)

		return -1;



	return 0;

}



static int resolve_procfd_symlink(int fd, char *buf, size_t buflen)

{

	int ret;

	char procfd[4096];



	ret = snprintf(procfd, 4096, "/proc/self/fd/%d", fd);

	if (ret < 0 || ret >= 4096)

		return -1;



	ret = readlink(procfd, buf, buflen);

	if (ret < 0 || (size_t)ret >= buflen)

		return -1;



	buf[ret] = '\0';



	return 0;

}



static int do_tiocgptpeer(char *ptmx, char *expected_procfd_contents)

{

	int ret;

	int master = -1, slave = -1, fret = -1;



	master = open(ptmx, O_RDWR | O_NOCTTY | O_CLOEXEC);

	if (master < 0) {

		fprintf(stderr, "Failed to open \"%s\": %s\n", ptmx,

			strerror(errno));

		return -1;

	}



	/*

	 * grantpt() makes assumptions about /dev/pts/ so ignore it. It's also

	 * not really needed.

	 */

	ret = unlockpt(master);

	if (ret < 0) {

		fprintf(stderr, "Failed to unlock terminal\n");

		goto do_cleanup;

	}



#ifdef TIOCGPTPEER

	slave = ioctl(master, TIOCGPTPEER, O_RDWR | O_NOCTTY | O_CLOEXEC);

#endif

	if (slave < 0) {

		if (errno == EINVAL) {

			fprintf(stderr, "TIOCGPTPEER is not supported. "

					"Skipping test.\n");

			fret = EXIT_SUCCESS;

		}



		fprintf(stderr, "Failed to perform TIOCGPTPEER ioctl\n");

		goto do_cleanup;

	}



	pid_t pid = fork();

	if (pid < 0)

		goto do_cleanup;



	if (pid == 0) {

		char buf[4096];



		ret = login_pty(slave);

		if (ret < 0) {

			fprintf(stderr, "Failed to setup terminal\n");

			_exit(EXIT_FAILURE);

		}



		ret = resolve_procfd_symlink(STDIN_FILENO, buf, sizeof(buf));

		if (ret < 0) {

			fprintf(stderr, "Failed to retrieve pathname of pts "

					"slave file descriptor\n");

			_exit(EXIT_FAILURE);

		}



		if (strncmp(expected_procfd_contents, buf,

			    strlen(expected_procfd_contents)) != 0) {

			fprintf(stderr, "Received invalid contents for "

					"\"/proc/<pid>/fd/%d\" symlink: %s\n",

					STDIN_FILENO, buf);

			_exit(-1);

		}



		fprintf(stderr, "Contents of \"/proc/<pid>/fd/%d\" "

				"symlink are valid: %s\n", STDIN_FILENO, buf);



		_exit(EXIT_SUCCESS);

	}



	ret = wait_for_pid(pid);

	if (ret < 0)

		goto do_cleanup;



	fret = EXIT_SUCCESS;



do_cleanup:

	if (master >= 0)

		close(master);

	if (slave >= 0)

		close(slave);



	return fret;

}



static int verify_non_standard_devpts_mount(void)

{

	char *mntpoint;

	int ret = -1;

	char devpts[] = P_tmpdir "/devpts_fs_XXXXXX";

	char ptmx[] = P_tmpdir "/devpts_fs_XXXXXX/ptmx";



	ret = umount("/dev/pts");

	if (ret < 0) {

		fprintf(stderr, "Failed to unmount \"/dev/pts\": %s\n",

				strerror(errno));

		return -1;

	}



	(void)umount("/dev/ptmx");



	mntpoint = mkdtemp(devpts);

	if (!mntpoint) {

		fprintf(stderr, "Failed to create temporary mountpoint: %s\n",

				 strerror(errno));

		return -1;

	}



	ret = mount("devpts", mntpoint, "devpts", MS_NOSUID | MS_NOEXEC,

		    "newinstance,ptmxmode=0666,mode=0620,gid=5");

	if (ret < 0) {

		fprintf(stderr, "Failed to mount devpts fs to \"%s\" in new "

				"mount namespace: %s\n", mntpoint,

				strerror(errno));

		unlink(mntpoint);

		return -1;

	}



	ret = snprintf(ptmx, sizeof(ptmx), "%s/ptmx", devpts);

	if (ret < 0 || (size_t)ret >= sizeof(ptmx)) {

		unlink(mntpoint);

		return -1;

	}



	ret = do_tiocgptpeer(ptmx, mntpoint);

	unlink(mntpoint);

	if (ret < 0)

		return -1;



	return 0;

}



static int verify_ptmx_bind_mount(void)

{

	int ret;



	ret = mount("/dev/pts/ptmx", "/dev/ptmx", NULL, MS_BIND, NULL);

	if (ret < 0) {

		fprintf(stderr, "Failed to bind mount \"/dev/pts/ptmx\" to "

				"\"/dev/ptmx\" mount namespace\n");

		return -1;

	}



	ret = do_tiocgptpeer("/dev/ptmx", "/dev/pts/");

	if (ret < 0)

		return -1;



	return 0;

}



static int verify_invalid_ptmx_bind_mount(void)

{

	int ret;

	char mntpoint_fd;

	char ptmx[] = P_tmpdir "/devpts_ptmx_XXXXXX";



	mntpoint_fd = mkstemp(ptmx);

	if (mntpoint_fd < 0) {

		fprintf(stderr, "Failed to create temporary directory: %s\n",

				 strerror(errno));

		return -1;

	}



	ret = mount("/dev/pts/ptmx", ptmx, NULL, MS_BIND, NULL);

	close(mntpoint_fd);

	if (ret < 0) {

		fprintf(stderr, "Failed to bind mount \"/dev/pts/ptmx\" to "

				"\"%s\" mount namespace\n", ptmx);

		return -1;

	}



	ret = do_tiocgptpeer(ptmx, "/dev/pts/");

	if (ret == 0)

		return -1;



	return 0;

}



int main(int argc, char *argv[])

{

	int ret;



	if (!isatty(STDIN_FILENO)) {

		fprintf(stderr, "Standard input file desciptor is not attached "

				"to a terminal. Skipping test\n");

		exit(EXIT_FAILURE);

	}



	ret = unshare(CLONE_NEWNS);

	if (ret < 0) {

		fprintf(stderr, "Failed to unshare mount namespace\n");

		exit(EXIT_FAILURE);

	}



	ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);

	if (ret < 0) {

		fprintf(stderr, "Failed to make \"/\" MS_PRIVATE in new mount "

				"namespace\n");

		exit(EXIT_FAILURE);

	}



	ret = verify_ptmx_bind_mount();

	if (ret < 0)

		exit(EXIT_FAILURE);



	ret = verify_invalid_ptmx_bind_mount();

	if (ret < 0)

		exit(EXIT_FAILURE);



	ret = verify_non_standard_devpts_mount();

	if (ret < 0)

		exit(EXIT_FAILURE);



	exit(EXIT_SUCCESS);

}

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