1 /*
2  * Copyright (C) 2012 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 /*
18  * Contributed by: Intel Corporation
19  */
20 
21 #include <gtest/gtest.h>
22 #include "BionicDeathTest.h"
23 
24 #include <pthread.h>
25 #include <stdint.h>
26 #include <stdio.h>
27 #include <unistd.h>
28 #include <set>
29 
30 #include "private/bionic_tls.h"
31 
32 extern "C" pid_t gettid(); // glibc defines this but doesn't declare it anywhere.
33 
34 #if defined(__BIONIC__)
35 extern uintptr_t __stack_chk_guard;
36 #endif
37 
38 struct stack_protector_checker {
39   std::set<pid_t> tids;
40   std::set<void*> guards;
41 
Checkstack_protector_checker42   void Check() {
43     pid_t tid = gettid();
44     void* guard = __get_tls()[TLS_SLOT_STACK_GUARD];
45 
46     printf("[thread %d] TLS stack guard = %p\n", tid, guard);
47 
48     // Duplicate tid. gettid(2) bug? Seeing this would be very upsetting.
49     ASSERT_TRUE(tids.find(tid) == tids.end());
50 
51     // Uninitialized guard. Our bug. Note this is potentially flaky; we _could_
52     // get four random zero bytes, but it should be vanishingly unlikely.
53     ASSERT_NE(guard, nullptr);
54 
55 #if defined(__BIONIC__)
56     // bionic always has the global too.
57     ASSERT_EQ(__stack_chk_guard, reinterpret_cast<uintptr_t>(guard));
58 #endif
59 
60     tids.insert(tid);
61     guards.insert(guard);
62   }
63 };
64 
TEST(stack_protector,same_guard_per_thread)65 TEST(stack_protector, same_guard_per_thread) {
66   // Everyone has the TLS slot set, even if their stack protector
67   // implementation doesn't yet use it.
68   stack_protector_checker checker;
69 
70   // Check the main thread.
71   ASSERT_EQ(getpid(), gettid()); // We are the main thread, right?
72   checker.Check();
73 
74   size_t thread_count = 9;
75   for (size_t i = 1; i < thread_count; ++i) {
76     pthread_t t;
77     ASSERT_EQ(0, pthread_create(&t, NULL, [](void* arg) -> void* {
78       stack_protector_checker* checker = reinterpret_cast<stack_protector_checker*>(arg);
79       checker->Check();
80       return nullptr;
81     }, &checker));
82     void* result;
83     ASSERT_EQ(0, pthread_join(t, &result));
84     ASSERT_EQ(NULL, result);
85   }
86   ASSERT_EQ(thread_count, checker.tids.size());
87 
88   // Both bionic and glibc use the same guard for every thread.
89   ASSERT_EQ(1U, checker.guards.size());
90 }
91 
TEST(stack_protector,global_guard)92 TEST(stack_protector, global_guard) {
93 #if defined(__BIONIC__)
94   // Bionic always has a global, even if it's using TLS.
95   ASSERT_NE(0, gettid());
96   ASSERT_NE(0U, __stack_chk_guard);
97 #else
98   GTEST_LOG_(INFO) << "glibc doesn't have a global __stack_chk_guard.\n";
99 #endif
100 }
101 
102 class stack_protector_DeathTest : public BionicDeathTest {};
103 
TEST_F(stack_protector_DeathTest,modify_stack_protector)104 TEST_F(stack_protector_DeathTest, modify_stack_protector) {
105   // In another file to prevent inlining, which removes stack protection.
106   extern void modify_stack_protector_test();
107   ASSERT_EXIT(modify_stack_protector_test(),
108               testing::KilledBySignal(SIGABRT), "stack corruption detected");
109 }
110