Add explicit memfd support to MemoryHeapBase
The default behavior of MemoryHeapBase is to request memory from
ashmem in libcutils. This library is being used to migrate from
ashmem to memfd, but on supported devices, memfd is still debug
only in order to sanitize expectations of callees of the library.
As such, we add a flag to explicitly request memfd files, as well
as to opt into file sealing of memfd files.
Note: the calling process will have to modify selinux permissions
to allow tmpfs access to the domains accessing the shared buffer.
This is more secure than ashmem as granular acess can be specified.
See audioserver_tmpfs in system/selinux for examples.
Test: Expected mappings recieved in Audioflinger for flag combos.
atest binderMemoryHeapBaseUnitTest
Change-Id: I893f7846f4d16b8ccc7f407fb957dccd9ebe62d7
diff --git a/libs/binder/tests/binderMemoryHeapBaseUnitTest.cpp b/libs/binder/tests/binderMemoryHeapBaseUnitTest.cpp
new file mode 100644
index 0000000..21cb70b
--- /dev/null
+++ b/libs/binder/tests/binderMemoryHeapBaseUnitTest.cpp
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * 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 <binder/MemoryHeapBase.h>
+#include <cutils/ashmem.h>
+#include <fcntl.h>
+
+#include <gtest/gtest.h>
+using namespace android;
+#ifdef __BIONIC__
+TEST(MemoryHeapBase, ForceMemfdRespected) {
+ auto mHeap = sp<MemoryHeapBase>::make(10, MemoryHeapBase::FORCE_MEMFD, "Test mapping");
+ int fd = mHeap->getHeapID();
+ EXPECT_NE(fd, -1);
+ EXPECT_FALSE(ashmem_valid(fd));
+ EXPECT_NE(fcntl(fd, F_GET_SEALS), -1);
+}
+
+TEST(MemoryHeapBase, MemfdSealed) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::FORCE_MEMFD,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ EXPECT_NE(fd, -1);
+ EXPECT_EQ(fcntl(fd, F_GET_SEALS), F_SEAL_SEAL);
+}
+
+TEST(MemoryHeapBase, MemfdUnsealed) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::FORCE_MEMFD |
+ MemoryHeapBase::MEMFD_ALLOW_SEALING,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ EXPECT_NE(fd, -1);
+ EXPECT_EQ(fcntl(fd, F_GET_SEALS), 0);
+}
+
+TEST(MemoryHeapBase, MemfdSealedProtected) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::FORCE_MEMFD |
+ MemoryHeapBase::READ_ONLY,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ EXPECT_NE(fd, -1);
+ EXPECT_EQ(fcntl(fd, F_GET_SEALS), F_SEAL_SEAL | F_SEAL_FUTURE_WRITE);
+}
+
+TEST(MemoryHeapBase, MemfdUnsealedProtected) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::FORCE_MEMFD |
+ MemoryHeapBase::READ_ONLY |
+ MemoryHeapBase::MEMFD_ALLOW_SEALING,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ EXPECT_NE(fd, -1);
+ EXPECT_EQ(fcntl(fd, F_GET_SEALS), F_SEAL_FUTURE_WRITE);
+}
+
+#else
+TEST(MemoryHeapBase, HostMemfdExpected) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::READ_ONLY,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ void* ptr = mHeap->getBase();
+ EXPECT_NE(ptr, MAP_FAILED);
+ EXPECT_TRUE(ashmem_valid(fd));
+ EXPECT_EQ(mHeap->getFlags(), MemoryHeapBase::READ_ONLY);
+}
+
+TEST(MemoryHeapBase,HostMemfdException) {
+ auto mHeap = sp<MemoryHeapBase>::make(8192,
+ MemoryHeapBase::FORCE_MEMFD |
+ MemoryHeapBase::READ_ONLY |
+ MemoryHeapBase::MEMFD_ALLOW_SEALING,
+ "Test mapping");
+ int fd = mHeap->getHeapID();
+ void* ptr = mHeap->getBase();
+ EXPECT_EQ(mHeap->getFlags(), MemoryHeapBase::READ_ONLY);
+ EXPECT_TRUE(ashmem_valid(fd));
+ EXPECT_NE(ptr, MAP_FAILED);
+}
+
+#endif