1// SPDX-License-Identifier: GPL-2.0
  2#define _GNU_SOURCE
  3#include <errno.h>
  4#include <fcntl.h>
  5#include <sched.h>
  6#include <stdbool.h>
  7#include <stdio.h>
  8#include <stdlib.h>
  9#include <string.h>
 10#include <unistd.h>
 11#include <asm/ioctls.h>
 12#include <sys/mount.h>
 13#include <sys/wait.h>
 14#include "../kselftest.h"
 15
 16static bool terminal_dup2(int duplicate, int original)
 17{
 18	int ret;
 19
 20	ret = dup2(duplicate, original);
 21	if (ret < 0)
 22		return false;
 23
 24	return true;
 25}
 26
 27static int terminal_set_stdfds(int fd)
 28{
 29	int i;
 30
 31	if (fd < 0)
 32		return 0;
 33
 34	for (i = 0; i < 3; i++)
 35		if (!terminal_dup2(fd, (int[]){STDIN_FILENO, STDOUT_FILENO,
 36					       STDERR_FILENO}[i]))
 37			return -1;
 38
 39	return 0;
 40}
 41
 42static int login_pty(int fd)
 43{
 44	int ret;
 45
 46	setsid();
 47
 48	ret = ioctl(fd, TIOCSCTTY, NULL);
 49	if (ret < 0)
 50		return -1;
 51
 52	ret = terminal_set_stdfds(fd);
 53	if (ret < 0)
 54		return -1;
 55
 56	if (fd > STDERR_FILENO)
 57		close(fd);
 58
 59	return 0;
 60}
 61
 62static int wait_for_pid(pid_t pid)
 63{
 64	int status, ret;
 65
 66again:
 67	ret = waitpid(pid, &status, 0);
 68	if (ret == -1) {
 69		if (errno == EINTR)
 70			goto again;
 71		return -1;
 72	}
 73	if (ret != pid)
 74		goto again;
 75
 76	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
 77		return -1;
 78
 79	return 0;
 80}
 81
 82static int resolve_procfd_symlink(int fd, char *buf, size_t buflen)
 83{
 84	int ret;
 85	char procfd[4096];
 86
 87	ret = snprintf(procfd, 4096, "/proc/self/fd/%d", fd);
 88	if (ret < 0 || ret >= 4096)
 89		return -1;
 90
 91	ret = readlink(procfd, buf, buflen);
 92	if (ret < 0 || (size_t)ret >= buflen)
 93		return -1;
 94
 95	buf[ret] = '\0';
 96
 97	return 0;
 98}
 99
100static int do_tiocgptpeer(char *ptmx, char *expected_procfd_contents)
101{
102	int ret;
103	int master = -1, slave = -1, fret = -1;
104
105	master = open(ptmx, O_RDWR | O_NOCTTY | O_CLOEXEC);
106	if (master < 0) {
107		fprintf(stderr, "Failed to open \"%s\": %s\n", ptmx,
108			strerror(errno));
109		return -1;
110	}
111
112	/*
113	 * grantpt() makes assumptions about /dev/pts/ so ignore it. It's also
114	 * not really needed.
115	 */
116	ret = unlockpt(master);
117	if (ret < 0) {
118		fprintf(stderr, "Failed to unlock terminal\n");
119		goto do_cleanup;
120	}
121
122#ifdef TIOCGPTPEER
123	slave = ioctl(master, TIOCGPTPEER, O_RDWR | O_NOCTTY | O_CLOEXEC);
124#endif
125	if (slave < 0) {
126		if (errno == EINVAL) {
127			fprintf(stderr, "TIOCGPTPEER is not supported. "
128					"Skipping test.\n");
129			fret = KSFT_SKIP;
130		} else {
131			fprintf(stderr,
132				"Failed to perform TIOCGPTPEER ioctl\n");
133			fret = EXIT_FAILURE;
134		}
135		goto do_cleanup;
136	}
137
138	pid_t pid = fork();
139	if (pid < 0)
140		goto do_cleanup;
141
142	if (pid == 0) {
143		char buf[4096];
144
145		ret = login_pty(slave);
146		if (ret < 0) {
147			fprintf(stderr, "Failed to setup terminal\n");
148			_exit(EXIT_FAILURE);
149		}
150
151		ret = resolve_procfd_symlink(STDIN_FILENO, buf, sizeof(buf));
152		if (ret < 0) {
153			fprintf(stderr, "Failed to retrieve pathname of pts "
154					"slave file descriptor\n");
155			_exit(EXIT_FAILURE);
156		}
157
158		if (strncmp(expected_procfd_contents, buf,
159			    strlen(expected_procfd_contents)) != 0) {
160			fprintf(stderr, "Received invalid contents for "
161					"\"/proc/<pid>/fd/%d\" symlink: %s\n",
162					STDIN_FILENO, buf);
163			_exit(-1);
164		}
165
166		fprintf(stderr, "Contents of \"/proc/<pid>/fd/%d\" "
167				"symlink are valid: %s\n", STDIN_FILENO, buf);
168
169		_exit(EXIT_SUCCESS);
170	}
171
172	ret = wait_for_pid(pid);
173	if (ret < 0)
174		goto do_cleanup;
175
176	fret = EXIT_SUCCESS;
177
178do_cleanup:
179	if (master >= 0)
180		close(master);
181	if (slave >= 0)
182		close(slave);
183
184	return fret;
185}
186
187static int verify_non_standard_devpts_mount(void)
188{
189	char *mntpoint;
190	int ret = -1;
191	char devpts[] = P_tmpdir "/devpts_fs_XXXXXX";
192	char ptmx[] = P_tmpdir "/devpts_fs_XXXXXX/ptmx";
193
194	ret = umount("/dev/pts");
195	if (ret < 0) {
196		fprintf(stderr, "Failed to unmount \"/dev/pts\": %s\n",
197				strerror(errno));
198		return -1;
199	}
200
201	(void)umount("/dev/ptmx");
202
203	mntpoint = mkdtemp(devpts);
204	if (!mntpoint) {
205		fprintf(stderr, "Failed to create temporary mountpoint: %s\n",
206				 strerror(errno));
207		return -1;
208	}
209
210	ret = mount("devpts", mntpoint, "devpts", MS_NOSUID | MS_NOEXEC,
211		    "newinstance,ptmxmode=0666,mode=0620,gid=5");
212	if (ret < 0) {
213		fprintf(stderr, "Failed to mount devpts fs to \"%s\" in new "
214				"mount namespace: %s\n", mntpoint,
215				strerror(errno));
216		unlink(mntpoint);
217		return -1;
218	}
219
220	ret = snprintf(ptmx, sizeof(ptmx), "%s/ptmx", devpts);
221	if (ret < 0 || (size_t)ret >= sizeof(ptmx)) {
222		unlink(mntpoint);
223		return -1;
224	}
225
226	ret = do_tiocgptpeer(ptmx, mntpoint);
227	unlink(mntpoint);
228	if (ret < 0)
229		return -1;
230
231	return 0;
232}
233
234static int verify_ptmx_bind_mount(void)
235{
236	int ret;
237
238	ret = mount("/dev/pts/ptmx", "/dev/ptmx", NULL, MS_BIND, NULL);
239	if (ret < 0) {
240		fprintf(stderr, "Failed to bind mount \"/dev/pts/ptmx\" to "
241				"\"/dev/ptmx\" mount namespace\n");
242		return -1;
243	}
244
245	ret = do_tiocgptpeer("/dev/ptmx", "/dev/pts/");
246	if (ret < 0)
247		return -1;
248
249	return 0;
250}
251
252static int verify_invalid_ptmx_bind_mount(void)
253{
254	int ret;
255	char mntpoint_fd;
256	char ptmx[] = P_tmpdir "/devpts_ptmx_XXXXXX";
257
258	mntpoint_fd = mkstemp(ptmx);
259	if (mntpoint_fd < 0) {
260		fprintf(stderr, "Failed to create temporary directory: %s\n",
261				 strerror(errno));
262		return -1;
263	}
264
265	ret = mount("/dev/pts/ptmx", ptmx, NULL, MS_BIND, NULL);
266	close(mntpoint_fd);
267	if (ret < 0) {
268		fprintf(stderr, "Failed to bind mount \"/dev/pts/ptmx\" to "
269				"\"%s\" mount namespace\n", ptmx);
270		return -1;
271	}
272
273	ret = do_tiocgptpeer(ptmx, "/dev/pts/");
274	if (ret == 0)
275		return -1;
276
277	return 0;
278}
279
280int main(int argc, char *argv[])
281{
282	int ret;
283
284	if (!isatty(STDIN_FILENO)) {
285		fprintf(stderr, "Standard input file descriptor is not attached "
286				"to a terminal. Skipping test\n");
287		exit(KSFT_SKIP);
288	}
289
290	ret = unshare(CLONE_NEWNS);
291	if (ret < 0) {
292		fprintf(stderr, "Failed to unshare mount namespace\n");
293		exit(EXIT_FAILURE);
294	}
295
296	ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
297	if (ret < 0) {
298		fprintf(stderr, "Failed to make \"/\" MS_PRIVATE in new mount "
299				"namespace\n");
300		exit(EXIT_FAILURE);
301	}
302
303	ret = verify_ptmx_bind_mount();
304	if (ret < 0)
305		exit(EXIT_FAILURE);
306
307	ret = verify_invalid_ptmx_bind_mount();
308	if (ret < 0)
309		exit(EXIT_FAILURE);
310
311	ret = verify_non_standard_devpts_mount();
312	if (ret < 0)
313		exit(EXIT_FAILURE);
314
315	exit(EXIT_SUCCESS);
316}