1 /*
2 * Copyright 2006, 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 #define LOG_TAG "crasher"
18
19 #include <assert.h>
20 #include <dirent.h>
21 #include <errno.h>
22 #include <fcntl.h>
23 #include <pthread.h>
24 #include <signal.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <sys/mman.h>
29 #include <sys/prctl.h>
30 #include <unistd.h>
31
32 // We test both kinds of logging.
33 #include <android-base/logging.h>
34 #include <log/log.h>
35
36 #include "seccomp_policy.h"
37
38 #if defined(STATIC_CRASHER)
39 #include "debuggerd/handler.h"
40 #endif
41
42 #if defined(__arm__)
43 // See https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt for details.
44 #define __kuser_helper_version (*(int32_t*) 0xffff0ffc)
45 typedef void * (__kuser_get_tls_t)(void);
46 #define __kuser_get_tls (*(__kuser_get_tls_t*) 0xffff0fe0)
47 typedef int (__kuser_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
48 #define __kuser_cmpxchg (*(__kuser_cmpxchg_t*) 0xffff0fc0)
49 typedef void (__kuser_dmb_t)(void);
50 #define __kuser_dmb (*(__kuser_dmb_t*) 0xffff0fa0)
51 typedef int (__kuser_cmpxchg64_t)(const int64_t*, const int64_t*, volatile int64_t*);
52 #define __kuser_cmpxchg64 (*(__kuser_cmpxchg64_t*) 0xffff0f60)
53 #endif
54
55 #define noinline __attribute__((__noinline__))
56
57 // Avoid name mangling so that stacks are more readable.
58 extern "C" {
59
60 void crash1(void);
61 void crashnostack(void);
62
63 int do_action(const char* arg);
64
maybe_abort()65 noinline void maybe_abort() {
66 if (time(0) != 42) {
67 abort();
68 }
69 }
70
71 char* smash_stack_dummy_buf;
smash_stack_dummy_function(volatile int * plen)72 noinline void smash_stack_dummy_function(volatile int* plen) {
73 smash_stack_dummy_buf[*plen] = 0;
74 }
75
76 // This must be marked with "__attribute__ ((noinline))", to ensure the
77 // compiler generates the proper stack guards around this function.
78 // Assign local array address to global variable to force stack guards.
79 // Use another noinline function to corrupt the stack.
smash_stack(volatile int * plen)80 noinline int smash_stack(volatile int* plen) {
81 printf("%s: deliberately corrupting stack...\n", getprogname());
82
83 char buf[128];
84 smash_stack_dummy_buf = buf;
85 // This should corrupt stack guards and make process abort.
86 smash_stack_dummy_function(plen);
87 return 0;
88 }
89
90 #pragma clang diagnostic push
91 #pragma clang diagnostic ignored "-Winfinite-recursion"
92
93 void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.
94
overflow_stack(void * p)95 noinline void overflow_stack(void* p) {
96 void* buf[1];
97 buf[0] = p;
98 global = buf;
99 overflow_stack(&buf);
100 }
101
102 #pragma clang diagnostic pop
103
thread_callback(void * raw_arg)104 noinline void* thread_callback(void* raw_arg) {
105 const char* arg = reinterpret_cast<const char*>(raw_arg);
106 return reinterpret_cast<void*>(static_cast<uintptr_t>(do_action(arg)));
107 }
108
do_action_on_thread(const char * arg)109 noinline int do_action_on_thread(const char* arg) {
110 pthread_t t;
111 pthread_create(&t, nullptr, thread_callback, const_cast<char*>(arg));
112 void* result = nullptr;
113 pthread_join(t, &result);
114 return reinterpret_cast<uintptr_t>(result);
115 }
116
crash_null()117 noinline int crash_null() {
118 int (*null_func)() = nullptr;
119 return null_func();
120 }
121
crash3(int a)122 noinline int crash3(int a) {
123 *reinterpret_cast<int*>(0xdead) = a;
124 return a*4;
125 }
126
crash2(int a)127 noinline int crash2(int a) {
128 a = crash3(a) + 2;
129 return a*3;
130 }
131
crash(int a)132 noinline int crash(int a) {
133 a = crash2(a) + 1;
134 return a*2;
135 }
136
abuse_heap()137 noinline void abuse_heap() {
138 char buf[16];
139 free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
140 }
141
leak()142 noinline void leak() {
143 while (true) {
144 void* mapping =
145 mmap(nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
146 static_cast<volatile char*>(mapping)[0] = 'a';
147 }
148 }
149
sigsegv_non_null()150 noinline void sigsegv_non_null() {
151 int* a = (int *)(&do_action);
152 *a = 42;
153 }
154
fprintf_null()155 noinline void fprintf_null() {
156 fprintf(nullptr, "oops");
157 }
158
readdir_null()159 noinline void readdir_null() {
160 readdir(nullptr);
161 }
162
strlen_null()163 noinline int strlen_null() {
164 char* sneaky_null = nullptr;
165 return strlen(sneaky_null);
166 }
167
usage()168 static int usage() {
169 fprintf(stderr, "usage: %s KIND\n", getprogname());
170 fprintf(stderr, "\n");
171 fprintf(stderr, "where KIND is:\n");
172 fprintf(stderr, " smash-stack overwrite a -fstack-protector guard\n");
173 fprintf(stderr, " stack-overflow recurse until the stack overflows\n");
174 fprintf(stderr, " nostack crash with a NULL stack pointer\n");
175 fprintf(stderr, "\n");
176 fprintf(stderr, " heap-usage cause a libc abort by abusing a heap function\n");
177 fprintf(stderr, " call-null cause a crash by calling through a nullptr\n");
178 fprintf(stderr, " leak leak memory until we get OOM-killed\n");
179 fprintf(stderr, "\n");
180 fprintf(stderr, " abort call abort()\n");
181 fprintf(stderr, " assert call assert() without a function\n");
182 fprintf(stderr, " assert2 call assert() with a function\n");
183 fprintf(stderr, " exit call exit(1)\n");
184 fprintf(stderr, "\n");
185 fprintf(stderr, " fortify fail a _FORTIFY_SOURCE check\n");
186 fprintf(stderr, " seccomp fail a seccomp check\n");
187 #if defined(__arm__)
188 fprintf(stderr, " kuser_helper_version call kuser_helper_version\n");
189 fprintf(stderr, " kuser_get_tls call kuser_get_tls\n");
190 fprintf(stderr, " kuser_cmpxchg call kuser_cmpxchg\n");
191 fprintf(stderr, " kuser_memory_barrier call kuser_memory_barrier\n");
192 fprintf(stderr, " kuser_cmpxchg64 call kuser_cmpxchg64\n");
193 #endif
194 fprintf(stderr, "\n");
195 fprintf(stderr, " LOG_ALWAYS_FATAL call liblog LOG_ALWAYS_FATAL\n");
196 fprintf(stderr, " LOG_ALWAYS_FATAL_IF call liblog LOG_ALWAYS_FATAL_IF\n");
197 fprintf(stderr, " LOG-FATAL call libbase LOG(FATAL)\n");
198 fprintf(stderr, "\n");
199 fprintf(stderr, " SIGFPE cause a SIGFPE\n");
200 fprintf(stderr, " SIGSEGV cause a SIGSEGV at address 0x0 (synonym: crash)\n");
201 fprintf(stderr, " SIGSEGV-non-null cause a SIGSEGV at a non-zero address\n");
202 fprintf(stderr, " SIGSEGV-unmapped mmap/munmap a region of memory and then attempt to access it\n");
203 fprintf(stderr, " SIGTRAP cause a SIGTRAP\n");
204 fprintf(stderr, "\n");
205 fprintf(stderr, " fprintf-NULL pass a null pointer to fprintf\n");
206 fprintf(stderr, " readdir-NULL pass a null pointer to readdir\n");
207 fprintf(stderr, " strlen-NULL pass a null pointer to strlen\n");
208 fprintf(stderr, " pthread_join-NULL pass a null pointer to pthread_join\n");
209 fprintf(stderr, "\n");
210 fprintf(stderr, " no_new_privs set PR_SET_NO_NEW_PRIVS and then abort\n");
211 fprintf(stderr, "\n");
212 fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n");
213 fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
214 fprintf(stderr, "all available file descriptors before crashing.\n");
215 fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n");
216
217 return EXIT_FAILURE;
218 }
219
do_action(const char * arg)220 noinline int do_action(const char* arg) {
221 // Prefixes.
222 if (!strncmp(arg, "wait-", strlen("wait-"))) {
223 char buf[1];
224 TEMP_FAILURE_RETRY(read(STDIN_FILENO, buf, sizeof(buf)));
225 return do_action(arg + strlen("wait-"));
226 } else if (!strncmp(arg, "exhaustfd-", strlen("exhaustfd-"))) {
227 errno = 0;
228 while (errno != EMFILE) {
229 open("/dev/null", O_RDONLY);
230 }
231 return do_action(arg + strlen("exhaustfd-"));
232 } else if (!strncmp(arg, "thread-", strlen("thread-"))) {
233 return do_action_on_thread(arg + strlen("thread-"));
234 }
235
236 // Actions.
237 if (!strcasecmp(arg, "SIGSEGV-non-null")) {
238 sigsegv_non_null();
239 } else if (!strcasecmp(arg, "smash-stack")) {
240 volatile int len = 128;
241 return smash_stack(&len);
242 } else if (!strcasecmp(arg, "stack-overflow")) {
243 overflow_stack(nullptr);
244 } else if (!strcasecmp(arg, "nostack")) {
245 crashnostack();
246 } else if (!strcasecmp(arg, "exit")) {
247 exit(1);
248 } else if (!strcasecmp(arg, "call-null")) {
249 return crash_null();
250 } else if (!strcasecmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) {
251 return crash(42);
252 } else if (!strcasecmp(arg, "abort")) {
253 maybe_abort();
254 } else if (!strcasecmp(arg, "assert")) {
255 __assert("some_file.c", 123, "false");
256 } else if (!strcasecmp(arg, "assert2")) {
257 __assert2("some_file.c", 123, "some_function", "false");
258 } else if (!strcasecmp(arg, "fortify")) {
259 char buf[10];
260 __read_chk(-1, buf, 32, 10);
261 while (true) pause();
262 } else if (!strcasecmp(arg, "LOG(FATAL)")) {
263 LOG(FATAL) << "hello " << 123;
264 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL")) {
265 LOG_ALWAYS_FATAL("hello %s", "world");
266 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL_IF")) {
267 LOG_ALWAYS_FATAL_IF(true, "hello %s", "world");
268 } else if (!strcasecmp(arg, "SIGFPE")) {
269 raise(SIGFPE);
270 return EXIT_SUCCESS;
271 } else if (!strcasecmp(arg, "SIGTRAP")) {
272 raise(SIGTRAP);
273 return EXIT_SUCCESS;
274 } else if (!strcasecmp(arg, "fprintf-NULL")) {
275 fprintf_null();
276 } else if (!strcasecmp(arg, "readdir-NULL")) {
277 readdir_null();
278 } else if (!strcasecmp(arg, "strlen-NULL")) {
279 return strlen_null();
280 } else if (!strcasecmp(arg, "pthread_join-NULL")) {
281 return pthread_join(0, nullptr);
282 } else if (!strcasecmp(arg, "heap-usage")) {
283 abuse_heap();
284 } else if (!strcasecmp(arg, "leak")) {
285 leak();
286 } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) {
287 char* map = reinterpret_cast<char*>(mmap(nullptr, sizeof(int), PROT_READ | PROT_WRITE,
288 MAP_SHARED | MAP_ANONYMOUS, -1, 0));
289 munmap(map, sizeof(int));
290 map[0] = '8';
291 } else if (!strcasecmp(arg, "seccomp")) {
292 set_system_seccomp_filter();
293 syscall(99999);
294 #if defined(__arm__)
295 } else if (!strcasecmp(arg, "kuser_helper_version")) {
296 return __kuser_helper_version;
297 } else if (!strcasecmp(arg, "kuser_get_tls")) {
298 return !__kuser_get_tls();
299 } else if (!strcasecmp(arg, "kuser_cmpxchg")) {
300 return __kuser_cmpxchg(0, 0, 0);
301 } else if (!strcasecmp(arg, "kuser_memory_barrier")) {
302 __kuser_dmb();
303 } else if (!strcasecmp(arg, "kuser_cmpxchg64")) {
304 return __kuser_cmpxchg64(0, 0, 0);
305 #endif
306 } else if (!strcasecmp(arg, "no_new_privs")) {
307 if (prctl(PR_SET_NO_NEW_PRIVS, 1) != 0) {
308 fprintf(stderr, "prctl(PR_SET_NO_NEW_PRIVS, 1) failed: %s\n", strerror(errno));
309 return EXIT_SUCCESS;
310 }
311 abort();
312 } else {
313 return usage();
314 }
315
316 fprintf(stderr, "%s: exiting normally!\n", getprogname());
317 return EXIT_SUCCESS;
318 }
319
main(int argc,char ** argv)320 int main(int argc, char** argv) {
321 #if defined(STATIC_CRASHER)
322 debuggerd_callbacks_t callbacks = {
323 .get_abort_message = []() {
324 static struct {
325 size_t size;
326 char msg[32];
327 } msg;
328
329 msg.size = strlen("dummy abort message");
330 memcpy(msg.msg, "dummy abort message", strlen("dummy abort message"));
331 return reinterpret_cast<abort_msg_t*>(&msg);
332 },
333 .post_dump = nullptr
334 };
335 debuggerd_init(&callbacks);
336 #endif
337
338 if (argc == 1) crash1();
339 else if (argc == 2) return do_action(argv[1]);
340
341 return usage();
342 }
343
344 };
345