4 files changed, 70 insertions, 0 deletions
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 94a582256..efed4aeb0 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -4247,10 +4247,12 @@ cc_binary(
         "//test/util:mount_util",
         "@com_google_absl//absl/strings",
         gtest,
+        "//test/util:cleanup",
         "//test/util:posix_error",
         "//test/util:temp_path",
         "//test/util:test_main",
         "//test/util:test_util",
+        "//test/util:thread_util",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/container:flat_hash_set",
     ],
diff --git a/test/syscalls/linux/cgroup.cc b/test/syscalls/linux/cgroup.cc
index 70ad5868f..a009ade7e 100644
--- a/test/syscalls/linux/cgroup.cc
+++ b/test/syscalls/linux/cgroup.cc
@@ -25,9 +25,11 @@
 #include "absl/strings/str_split.h"
 #include "test/util/capability_util.h"
 #include "test/util/cgroup_util.h"
+#include "test/util/cleanup.h"
 #include "test/util/mount_util.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
+#include "test/util/thread_util.h"
 
 namespace gvisor {
 namespace testing {
@@ -192,6 +194,56 @@ TEST(Cgroup, MoptAllMustBeExclusive) {
       SyscallFailsWithErrno(EINVAL));
 }
 
+TEST(Cgroup, MountRace) {
+  SKIP_IF(!CgroupsAvailable());
+
+  TempPath mountpoint = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+
+  const DisableSave ds;  // Too many syscalls.
+
+  auto mount_thread = [&mountpoint]() {
+    for (int i = 0; i < 100; ++i) {
+      mount("none", mountpoint.path().c_str(), "cgroup", 0, 0);
+    }
+  };
+  std::list<ScopedThread> threads;
+  for (int i = 0; i < 10; ++i) {
+    threads.emplace_back(mount_thread);
+  }
+  for (auto& t : threads) {
+    t.Join();
+  }
+
+  auto cleanup = Cleanup([&mountpoint] {
+    // We need 1 umount call per successful mount. If some of the mount calls
+    // were unsuccessful, their corresponding umount will silently fail.
+    for (int i = 0; i < (10 * 100) + 1; ++i) {
+      umount(mountpoint.path().c_str());
+    }
+  });
+
+  Cgroup c = Cgroup(mountpoint.path());
+  // c should be a valid cgroup.
+  EXPECT_NO_ERRNO(c.ContainsCallingProcess());
+}
+
+TEST(Cgroup, UnmountRepeated) {
+  SKIP_IF(!CgroupsAvailable());
+
+  const DisableSave ds;  // Too many syscalls.
+
+  Mounter m(ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir()));
+  Cgroup c = ASSERT_NO_ERRNO_AND_VALUE(m.MountCgroupfs(""));
+
+  // First unmount should succeed.
+  EXPECT_THAT(umount(c.Path().c_str()), SyscallSucceeds());
+
+  // We just manually unmounted, so release managed resources.
+  m.release(c);
+
+  EXPECT_THAT(umount(c.Path().c_str()), SyscallFailsWithErrno(EINVAL));
+}
+
 TEST(MemoryCgroup, MemoryUsageInBytes) {
   SKIP_IF(!CgroupsAvailable());
 
diff --git a/test/util/cgroup_util.cc b/test/util/cgroup_util.cc
index 04d4f8de0..977993f41 100644
--- a/test/util/cgroup_util.cc
+++ b/test/util/cgroup_util.cc
@@ -142,6 +142,20 @@ PosixError Mounter::Unmount(const Cgroup& c) {
   return NoError();
 }
 
+void Mounter::release(const Cgroup& c) {
+  auto mp = mountpoints_.find(c.id());
+  if (mp != mountpoints_.end()) {
+    mp->second.release();
+    mountpoints_.erase(mp);
+  }
+
+  auto m = mounts_.find(c.id());
+  if (m != mounts_.end()) {
+    m->second.Release();
+    mounts_.erase(m);
+  }
+}
+
 constexpr char kProcCgroupsHeader[] =
     "#subsys_name\thierarchy\tnum_cgroups\tenabled";
 
diff --git a/test/util/cgroup_util.h b/test/util/cgroup_util.h
index b797a8b24..e3f696a89 100644
--- a/test/util/cgroup_util.h
+++ b/test/util/cgroup_util.h
@@ -83,6 +83,8 @@ class Mounter {
 
   PosixError Unmount(const Cgroup& c);
 
+  void release(const Cgroup& c);
+
  private:
   // The destruction order of these members avoids errors during cleanup. We
   // first unmount (by executing the mounts_ cleanups), then delete the