binderfs_test: switch from /dev to a unique per-test mountpoint

Unprivileged users will be able to create directories in there. The
unprivileged test for /dev wouldn't have worked on most systems.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200313152420.138777-2-christian.brauner@ubuntu.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c
index 0cfca65e095ae88f20ce6a3a334425d54a7dacaf..818eb49f8125375abe64823ddb4ecab42793e055 100644 (file)
--- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c
+++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c
@@ -139,29 +139,25 @@ static int __do_binderfs_test(void)
        int fd, ret, saved_errno;
        size_t len;
        ssize_t wret;
-       bool keep = false;
        struct binderfs_device device = { 0 };
        struct binder_version version = { 0 };
+       char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
+               device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
 
        change_to_mountns();
 
-       ret = mkdir("/dev/binderfs", 0755);
-       if (ret < 0) {
-               if (errno != EEXIST)
-                       ksft_exit_fail_msg(
-                               "%s - Failed to create binderfs mountpoint\n",
-                               strerror(errno));
-
-               keep = true;
-       }
+       if (!mkdtemp(binderfs_mntpt))
+               ksft_exit_fail_msg(
+                       "%s - Failed to create binderfs mountpoint\n",
+                       strerror(errno));
 
-       ret = mount(NULL, "/dev/binderfs", "binder", 0, 0);
+       ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
        if (ret < 0) {
                if (errno != ENODEV)
                        ksft_exit_fail_msg("%s - Failed to mount binderfs\n",
                                           strerror(errno));
 
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                return 1;
        }
 
@@ -170,7 +166,8 @@ static int __do_binderfs_test(void)
 
        memcpy(device.name, "my-binder", strlen("my-binder"));
 
-       fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC);
+       snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
+       fd = open(device_path, O_RDONLY | O_CLOEXEC);
        if (fd < 0)
                ksft_exit_fail_msg(
                        "%s - Failed to open binder-control device\n",
@@ -181,7 +178,7 @@ static int __do_binderfs_test(void)
        close(fd);
        errno = saved_errno;
        if (ret < 0) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg(
                        "%s - Failed to allocate new binder device\n",
                        strerror(errno));
@@ -194,9 +191,10 @@ static int __do_binderfs_test(void)
        /* binder device allocation test passed */
        ksft_inc_pass_cnt();
 
-       fd = open("/dev/binderfs/my-binder", O_CLOEXEC | O_RDONLY);
+       snprintf(device_path, sizeof(device_path), "%s/my-binder", binderfs_mntpt);
+       fd = open(device_path, O_CLOEXEC | O_RDONLY);
        if (fd < 0) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg("%s - Failed to open my-binder device\n",
                                   strerror(errno));
        }
@@ -206,7 +204,7 @@ static int __do_binderfs_test(void)
        close(fd);
        errno = saved_errno;
        if (ret < 0) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg(
                        "%s - Failed to open perform BINDER_VERSION request\n",
                        strerror(errno));
@@ -218,9 +216,9 @@ static int __do_binderfs_test(void)
        /* binder transaction with binderfs binder device passed */
        ksft_inc_pass_cnt();
 
-       ret = unlink("/dev/binderfs/my-binder");
+       ret = unlink(device_path);
        if (ret < 0) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg("%s - Failed to delete binder device\n",
                                   strerror(errno));
        }
@@ -228,12 +226,13 @@ static int __do_binderfs_test(void)
        /* binder device removal passed */
        ksft_inc_pass_cnt();
 
-       ret = unlink("/dev/binderfs/binder-control");
+       snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
+       ret = unlink(device_path);
        if (!ret) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg("Managed to delete binder-control device\n");
        } else if (errno != EPERM) {
-               keep ? : rmdir_protect_errno("/dev/binderfs");
+               rmdir_protect_errno(binderfs_mntpt);
                ksft_exit_fail_msg(
                        "%s - Failed to delete binder-control device but exited with unexpected error code\n",
                        strerror(errno));
@@ -243,8 +242,8 @@ static int __do_binderfs_test(void)
        ksft_inc_xfail_cnt();
 
 on_error:
-       ret = umount2("/dev/binderfs", MNT_DETACH);
-       keep ?: rmdir_protect_errno("/dev/binderfs");
+       ret = umount2(binderfs_mntpt, MNT_DETACH);
+       rmdir_protect_errno(binderfs_mntpt);
        if (ret < 0)
                ksft_exit_fail_msg("%s - Failed to unmount binderfs\n",
                                   strerror(errno));