1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <android-base/hex.h>
18 #include <android-base/logging.h>
19 #include <binder/Binder.h>
20 #include <binder/IBinder.h>
21 #include <binder/IPCThreadState.h>
22 #include <binder/IServiceManager.h>
23 #include <binder/Parcel.h>
24 #include <binder/Stability.h>
25 #include <gtest/gtest.h>
26
27 #include <sys/prctl.h>
28 #include <thread>
29
30 using namespace android;
31
32 const String16 kServerName = String16("binderClearBuf");
33
34 class FooBar : public BBinder {
35 public:
36 enum {
37 TRANSACTION_REPEAT_STRING = IBinder::FIRST_CALL_TRANSACTION,
38 };
39
40 std::mutex foo;
41 std::string last;
42
onTransact(uint32_t code,const Parcel & data,Parcel * reply,uint32_t flags)43 status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags) {
44 // not checking data, since there is no hook at the time this test is
45 // written to check values there are set to zero. Instead, we only check
46 // the reply parcel.
47
48 switch (code) {
49 case TRANSACTION_REPEAT_STRING: {
50 const char* str = data.readCString();
51 return reply->writeCString(str == nullptr ? "<null>" : str);
52 }
53 }
54 return BBinder::onTransact(code, data, reply, flags);
55 }
RepeatString(const sp<IBinder> binder,const std::string & repeat,std::string * outBuffer)56 static std::string RepeatString(const sp<IBinder> binder,
57 const std::string& repeat,
58 std::string* outBuffer) {
59 Parcel data;
60 data.writeCString(repeat.c_str());
61 std::string result;
62 const uint8_t* lastReply;
63 size_t lastReplySize;
64 {
65 Parcel reply;
66 binder->transact(TRANSACTION_REPEAT_STRING, data, &reply, FLAG_CLEAR_BUF);
67 result = reply.readCString();
68 lastReply = reply.data();
69 lastReplySize = reply.dataSize();
70 }
71 *outBuffer = android::base::HexString(lastReply, lastReplySize);
72 return result;
73 }
74 };
75
TEST(BinderClearBuf,ClearKernelBuffer)76 TEST(BinderClearBuf, ClearKernelBuffer) {
77 sp<IBinder> binder = defaultServiceManager()->getService(kServerName);
78 ASSERT_NE(nullptr, binder);
79
80 std::string replyBuffer;
81 std::string result = FooBar::RepeatString(binder, "foo", &replyBuffer);
82 EXPECT_EQ("foo", result);
83
84 // the buffer must have at least some length for the string, but we will
85 // just check it has some length, to avoid assuming anything about the
86 // format
87 EXPECT_GT(replyBuffer.size(), 0);
88
89 for (size_t i = 0; i < replyBuffer.size(); i++) {
90 EXPECT_EQ(replyBuffer[i], '0') << "reply buffer at " << i;
91 }
92 }
93
main(int argc,char ** argv)94 int main(int argc, char** argv) {
95 ::testing::InitGoogleTest(&argc, argv);
96
97 if (fork() == 0) {
98 prctl(PR_SET_PDEATHSIG, SIGHUP);
99
100 sp<IBinder> server = new FooBar;
101 android::defaultServiceManager()->addService(kServerName, server);
102
103 IPCThreadState::self()->joinThreadPool(true);
104 exit(1); // should not reach
105 }
106
107 // This is not racey. Just giving these services some time to register before we call
108 // getService which sleeps for much longer. One alternative would be to
109 // start a threadpool + use waitForService, but we want to have as few
110 // binder things going on in this test as possible, since we are checking
111 // memory is zero'd which the kernel has a right to change.
112 usleep(100000);
113
114 return RUN_ALL_TESTS();
115 }
116