From ce290a19609d5ecd4a240a4750e0ed9a476cf015 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 13 Mar 2018 17:55:27 +0100 Subject: 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: Christian Brauner Acked-by: "Eric W. Biederman" Acked-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- tools/testing/selftests/filesystems/.gitignore | 1 + tools/testing/selftests/filesystems/Makefile | 2 +- tools/testing/selftests/filesystems/devpts_pts.c | 313 +++++++++++++++++++++++ 3 files changed, 315 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/filesystems/devpts_pts.c (limited to 'tools/testing/selftests/filesystems') diff --git a/tools/testing/selftests/filesystems/.gitignore b/tools/testing/selftests/filesystems/.gitignore index 31d6e426b6d4..8449cf6716ce 100644 --- a/tools/testing/selftests/filesystems/.gitignore +++ b/tools/testing/selftests/filesystems/.gitignore @@ -1 +1,2 @@ dnotify_test +devpts_pts diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile index 13a73bf725b5..4e6d09fb166f 100644 --- a/tools/testing/selftests/filesystems/Makefile +++ b/tools/testing/selftests/filesystems/Makefile @@ -1,5 +1,5 @@ # SPDX-License-Identifier: GPL-2.0 -TEST_PROGS := dnotify_test +TEST_PROGS := dnotify_test devpts_pts all: $(TEST_PROGS) include ../lib.mk diff --git a/tools/testing/selftests/filesystems/devpts_pts.c b/tools/testing/selftests/filesystems/devpts_pts.c new file mode 100644 index 000000000000..b9055e974289 --- /dev/null +++ b/tools/testing/selftests/filesystems/devpts_pts.c @@ -0,0 +1,313 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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//fd/%d\" symlink: %s\n", + STDIN_FILENO, buf); + _exit(-1); + } + + fprintf(stderr, "Contents of \"/proc//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); +} -- cgit v1.2.3-59-g8ed1b