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Subject[PATCH 3/3 v2] selftests: add devpts selftests
Date
This adds a simple test to check whether /proc/<pid>/fd/<nr> symlinks are
correctly pointing to /dev/pts/<idx> devices when attached to a terminal.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
ChangeLog v1->v2:
* patch added
ChangeLog v0->v1:
* patch not present
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/filesystems/.gitignore | 1 +
tools/testing/selftests/filesystems/Makefile | 3 +-
tools/testing/selftests/filesystems/devpts_pts.c | 191 +++++++++++++++++++++++
4 files changed, 195 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/filesystems/devpts_pts.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 7442dfb73b7f..dbda89c9d9b9 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -7,6 +7,7 @@ TARGETS += cpufreq
TARGETS += cpu-hotplug
TARGETS += efivarfs
TARGETS += exec
+TARGETS += filesystems
TARGETS += firmware
TARGETS += ftrace
TARGETS += futex
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..b9b5d2f68990 100644
--- a/tools/testing/selftests/filesystems/Makefile
+++ b/tools/testing/selftests/filesystems/Makefile
@@ -1,5 +1,6 @@
# 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..10a73e422600
--- /dev/null
+++ b/tools/testing/selftests/filesystems/devpts_pts.c
@@ -0,0 +1,191 @@
+// 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 lxc_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 = lxc_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;
+}
+
+int main(int argc, char *argv[])
+{
+ int master = -1, ret = -1, slave = -1;
+ int fret = EXIT_FAILURE;
+
+ if (!isatty(STDIN_FILENO)) {
+ fprintf(stderr, "Standard input file desciptor is not attached "
+ "to a terminal. Skipping test\n");
+ goto do_cleanup;
+ }
+
+ ret = unshare(CLONE_NEWNS);
+ if (ret < 0) {
+ fprintf(stderr, "Failed to unshare mount namespace\n");
+ goto do_cleanup;
+ }
+
+ ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+ if (ret < 0) {
+ fprintf(stderr, "Failed to make \"/\" MS_PRIVATE in new mount "
+ "namespace\n");
+ goto do_cleanup;
+ }
+
+ 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");
+ goto do_cleanup;
+ }
+
+ master = open("/dev/ptmx", O_RDWR | O_NOCTTY | O_CLOEXEC);
+ if (master < 0) {
+ fprintf(stderr, "Failed to open \"/dev/ptmx\"\n");
+ goto do_cleanup;
+ }
+
+ ret = grantpt(master);
+ if (ret < 0) {
+ fprintf(stderr, "Failed to grant access to terminal\n");
+ goto do_cleanup;
+ }
+
+ 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 = readlink("/proc/self/fd/0", buf, sizeof(buf));
+ if (ret < 0 || (size_t)ret >= sizeof(buf)) {
+ fprintf(stderr, "Failed to retrieve pathname of pts "
+ "slave file descriptor\n");
+ _exit(EXIT_FAILURE);
+ }
+ buf[ret] = '\0';
+
+ if (strncmp(buf, "/dev/pts/", strlen("/dev/pts/"))) {
+ fprintf(stderr, "Received invalid contents for "
+ "\"/proc/<pid>/fd/<nr>\" symlink: %s\n",
+ buf);
+ _exit(-1);
+ }
+
+ fprintf(stderr, "Contents of \"/proc/<pid>/fd/<nr>\" "
+ "symlink are valid: %s\n", 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 ret;
+}
--
2.15.1
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