317 lines · c
1// SPDX-License-Identifier: GPL-2.02#define _GNU_SOURCE3#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 also114 * 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 TIOCGPTPEER123 slave = ioctl(master, TIOCGPTPEER, O_RDWR | O_NOCTTY | O_CLOEXEC);124#endif125 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}317