Allow user mount for verity fs

Allow user mounting a verity fs on an existing mount by specifying mount
flags root_hash and lower_path.

PiperOrigin-RevId: 366843846

2 files changed, 67 insertions, 0 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index a9fa93437..4571c706b 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -1304,6 +1304,20 @@ cc_binary(
 )
 
 cc_binary(
+    name = "verity_mount_test",
+    testonly = 1,
+    srcs = ["verity_mount.cc"],
+    linkstatic = 1,
+    deps = [
+        gtest,
+        "//test/util:capability_util",
+        "//test/util:temp_path",
+        "//test/util:test_main",
+        "//test/util:test_util",
+    ],
+)
+
+cc_binary(
     name = "mremap_test",
     testonly = 1,
     srcs = ["mremap.cc"],
diff --git a/test/syscalls/linux/verity_mount.cc b/test/syscalls/linux/verity_mount.cc
new file mode 100644
index 000000000..e73dd5599
--- /dev/null
+++ b/test/syscalls/linux/verity_mount.cc
@@ -0,0 +1,53 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/mount.h>
+
+#include <iomanip>
+#include <sstream>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "test/util/capability_util.h"
+#include "test/util/temp_path.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+// Mount verity file system on an existing gofer mount.
+TEST(MountTest, MountExisting) {
+  // Verity is implemented in VFS2.
+  SKIP_IF(IsRunningWithVFS1());
+
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
+
+  // Mount a new tmpfs file system.
+  auto const tmpfs_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  ASSERT_THAT(mount("", tmpfs_dir.path().c_str(), "tmpfs", 0, ""),
+              SyscallSucceeds());
+
+  // Mount a verity file system on the existing gofer mount.
+  auto const verity_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  std::string opts = "lower_path=" + tmpfs_dir.path();
+  EXPECT_THAT(mount("", verity_dir.path().c_str(), "verity", 0, opts.c_str()),
+              SyscallSucceeds());
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor