[PATCH review 02/18] mnt: Update unprivileged remount test

Eric W. Biederman
2014-12-12T22:51:16Z

- MNT_NODEV should be irrelevant except when reading back mount flags,
no longer specify MNT_NODEV on remount.

- Test MNT_NODEV on devpts where it is meaningful even for unprivileged mounts.

- Add a test to verify that remount of a prexisting mount with the same flags
is allowed and does not change those flags.

- Cleanup up the definitions of MS_REC, MS_RELATIME, MS_STRICTATIME that are used
when the code is built in an environment without them.

- Correct the test error messages when tests fail. There were not 5 tests
that tested MS_RELATIME.

Cc: stable@vger.kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
.../selftests/mount/unprivileged-remount-test.c | 172 +++++++++++++++++----
1 file changed, 142 insertions(+), 30 deletions(-)

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 1b3ff2fda4d0..9669d375625a 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -6,6 +6,8 @@
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/wait.h>
+#include <sys/vfs.h>
+#include <sys/statvfs.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
@@ -32,11 +34,14 @@
# define CLONE_NEWPID 0x20000000
#endif

+#ifndef MS_REC
+# define MS_REC 16384
+#endif
#ifndef MS_RELATIME
-#define MS_RELATIME (1 << 21)
+# define MS_RELATIME (1 << 21)
#endif
#ifndef MS_STRICTATIME
-#define MS_STRICTATIME (1 << 24)
+# define MS_STRICTATIME (1 << 24)
#endif

static void die(char *fmt, ...)
@@ -87,6 +92,45 @@ static void write_file(char *filename, char *fmt, ...)
}
}

+static int read_mnt_flags(const char *path)
+{
+ int ret;
+ struct statvfs stat;
+ int mnt_flags;
+
+ ret = statvfs(path, &stat);
+ if (ret != 0) {
+ die("statvfs of %s failed: %s\n",
+ path, strerror(errno));
+ }
+ if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | \
+ ST_NOEXEC | ST_NOATIME | ST_NODIRATIME | ST_RELATIME | \
+ ST_SYNCHRONOUS | ST_MANDLOCK)) {
+ die("Unrecognized mount flags\n");
+ }
+ mnt_flags = 0;
+ if (stat.f_flag & ST_RDONLY)
+ mnt_flags |= MS_RDONLY;
+ if (stat.f_flag & ST_NOSUID)
+ mnt_flags |= MS_NOSUID;
+ if (stat.f_flag & ST_NODEV)
+ mnt_flags |= MS_NODEV;
+ if (stat.f_flag & ST_NOEXEC)
+ mnt_flags |= MS_NOEXEC;
+ if (stat.f_flag & ST_NOATIME)
+ mnt_flags |= MS_NOATIME;
+ if (stat.f_flag & ST_NODIRATIME)
+ mnt_flags |= MS_NODIRATIME;
+ if (stat.f_flag & ST_RELATIME)
+ mnt_flags |= MS_RELATIME;
+ if (stat.f_flag & ST_SYNCHRONOUS)
+ mnt_flags |= MS_SYNCHRONOUS;
+ if (stat.f_flag & ST_MANDLOCK)
+ mnt_flags |= ST_MANDLOCK;
+
+ return mnt_flags;
+}
+
static void create_and_enter_userns(void)
{
uid_t uid;
@@ -118,7 +162,8 @@ static void create_and_enter_userns(void)
}

static
-bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
+bool test_unpriv_remount(const char *fstype, const char *mount_options,
+ int mount_flags, int remount_flags, int invalid_flags)
{
pid_t child;

@@ -151,9 +196,11 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
strerror(errno));
}

- if (mount("testing", "/tmp", "ramfs", mount_flags, NULL) != 0) {
- die("mount of /tmp failed: %s\n",
- strerror(errno));
+ if (mount("testing", "/tmp", fstype, mount_flags, mount_options) != 0) {
+ die("mount of %s with options '%s' on /tmp failed: %s\n",
+ fstype,
+ mount_options? mount_options : "",
+ strerror(errno));
}

create_and_enter_userns();
@@ -181,62 +228,127 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)

static bool test_unpriv_remount_simple(int mount_flags)
{
- return test_unpriv_remount(mount_flags, mount_flags, 0);
+ return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags, 0);
}

static bool test_unpriv_remount_atime(int mount_flags, int invalid_flags)
{
- return test_unpriv_remount(mount_flags, mount_flags, invalid_flags);
+ return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags,
+ invalid_flags);
+}
+
+static bool test_priv_mount_unpriv_remount(void)
+{
+ pid_t child;
+ int ret;
+ const char *orig_path = "/dev";
+ const char *dest_path = "/tmp";
+ int orig_mnt_flags, remount_mnt_flags;
+
+ child = fork();
+ if (child == -1) {
+ die("fork failed: %s\n",
+ strerror(errno));
+ }
+ if (child != 0) { /* parent */
+ pid_t pid;
+ int status;
+ pid = waitpid(child, &status, 0);
+ if (pid == -1) {
+ die("waitpid failed: %s\n",
+ strerror(errno));
+ }
+ if (pid != child) {
+ die("waited for %d got %d\n",
+ child, pid);
+ }
+ if (!WIFEXITED(status)) {
+ die("child did not terminate cleanly\n");
+ }
+ return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
+ }
+
+ orig_mnt_flags = read_mnt_flags(orig_path);
+
+ create_and_enter_userns();
+ ret = unshare(CLONE_NEWNS);
+ if (ret != 0) {
+ die("unshare(CLONE_NEWNS) failed: %s\n",
+ strerror(errno));
+ }
+
+ ret = mount(orig_path, dest_path, "bind", MS_BIND | MS_REC, NULL);
+ if (ret != 0) {
+ die("recursive bind mount of %s onto %s failed: %s\n",
+ orig_path, dest_path, strerror(errno));
+ }
+
+ ret = mount(dest_path, dest_path, "none",
+ MS_REMOUNT | MS_BIND | orig_mnt_flags , NULL);
+ if (ret != 0) {
+ /* system("cat /proc/self/mounts"); */
+ die("remount of /tmp failed: %s\n",
+ strerror(errno));
+ }
+
+ remount_mnt_flags = read_mnt_flags(dest_path);
+ if (orig_mnt_flags != remount_mnt_flags) {
+ die("Mount flags unexpectedly changed during remount of %s originally mounted on %s\n",
+ dest_path, orig_path);
+ }
+ exit(EXIT_SUCCESS);
}

int main(int argc, char **argv)
{
- if (!test_unpriv_remount_simple(MS_RDONLY|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_RDONLY)) {
die("MS_RDONLY malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NODEV)) {
+ if (!test_unpriv_remount("devpts", "newinstance", MS_NODEV, MS_NODEV, 0)) {
die("MS_NODEV malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NOSUID|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_NOSUID)) {
die("MS_NOSUID malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NOEXEC|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_NOEXEC)) {
die("MS_NOEXEC malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_RELATIME,
+ MS_NOATIME))
{
die("MS_RELATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_STRICTATIME,
+ MS_NOATIME))
{
die("MS_STRICTATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODEV,
- MS_STRICTATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_NOATIME,
+ MS_STRICTATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_NOATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME,
+ MS_NOATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_RELATIME|MS_NODIRATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME,
+ MS_NOATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_STRICTATIME|MS_NODIRATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME|MS_NODEV,
- MS_STRICTATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME,
+ MS_STRICTATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_NOATIME|MS_DIRATIME malfunctions\n");
}
- if (!test_unpriv_remount(MS_STRICTATIME|MS_NODEV, MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount("ramfs", NULL, MS_STRICTATIME, 0, MS_NOATIME))
{
die("Default atime malfunctions\n");
}
+ if (!test_priv_mount_unpriv_remount()) {
+ die("Mount flags unexpectedly changed after remount\n");
+ }
return EXIT_SUCCESS;
}
--
1.9.1