[PATCH 4/4 v5] selftests: add devpts selftests

[Christian Brauner]

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 
---
ChangeLog v4->v5:
* extend tests to verify failure on ptmx devices located outside the
  devpts mount without a common ancestor directory
ChangeLog v3->v4:
* patch unchanged
ChangeLog v2->v3:
* extend test for non-standard devpts mounts such as
  mount -t devpts e devpts /mnt
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 |   2 +-
 tools/testing/selftests/filesystems/devpts_pts.c | 313 +++
 4 files changed, 316 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..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 ..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, , 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, 

[PATCH 4/4 v5] selftests: add devpts selftests

[Christian Brauner]

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 
---
ChangeLog v4->v5:
* extend tests to verify failure on ptmx devices located outside the
  devpts mount without a common ancestor directory
ChangeLog v3->v4:
* patch unchanged
ChangeLog v2->v3:
* extend test for non-standard devpts mounts such as
  mount -t devpts e devpts /mnt
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 |   2 +-
 tools/testing/selftests/filesystems/devpts_pts.c | 313 +++
 4 files changed, 316 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..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 ..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, , 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);