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 <error.h>
23 #include <fcntl.h>
24 #include <pthread.h>
25 #include <signal.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <sys/mman.h>
30 #include <sys/prctl.h>
31 #include <unistd.h>
32
33 #include <android-base/file.h>
34 #include <android-base/strings.h>
35
36 // We test both kinds of logging.
37 #include <android-base/logging.h>
38 #include <log/log.h>
39
40 #include "seccomp_policy.h"
41
42 #if defined(STATIC_CRASHER)
43 #include "debuggerd/handler.h"
44 #endif
45
46 extern "C" void android_set_abort_message(const char* msg);
47
48 #if defined(__arm__)
49 // See https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt for details.
50 #define __kuser_helper_version (*(int32_t*) 0xffff0ffc)
51 typedef void * (__kuser_get_tls_t)(void);
52 #define __kuser_get_tls (*(__kuser_get_tls_t*) 0xffff0fe0)
53 typedef int (__kuser_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
54 #define __kuser_cmpxchg (*(__kuser_cmpxchg_t*) 0xffff0fc0)
55 typedef void (__kuser_dmb_t)(void);
56 #define __kuser_dmb (*(__kuser_dmb_t*) 0xffff0fa0)
57 typedef int (__kuser_cmpxchg64_t)(const int64_t*, const int64_t*, volatile int64_t*);
58 #define __kuser_cmpxchg64 (*(__kuser_cmpxchg64_t*) 0xffff0f60)
59 #endif
60
61 #define noinline __attribute__((__noinline__))
62
63 // Avoid name mangling so that stacks are more readable.
64 extern "C" {
65
66 void crash1();
67 void crash_no_stack();
68 void crash_bti();
69 void crash_pac();
70
71 int do_action(const char* arg);
72
maybe_abort()73 noinline void maybe_abort() {
74 if (time(0) != 42) {
75 abort();
76 }
77 }
78
79 char* smash_stack_dummy_buf;
smash_stack_dummy_function(volatile int * plen)80 noinline void smash_stack_dummy_function(volatile int* plen) {
81 smash_stack_dummy_buf[*plen] = 0;
82 }
83
84 // This must be marked with "__attribute__ ((noinline))", to ensure the
85 // compiler generates the proper stack guards around this function.
86 // Assign local array address to global variable to force stack guards.
87 // Use another noinline function to corrupt the stack.
smash_stack(volatile int * plen)88 noinline int smash_stack(volatile int* plen) {
89 printf("%s: deliberately corrupting stack...\n", getprogname());
90
91 char buf[128];
92 smash_stack_dummy_buf = buf;
93 // This should corrupt stack guards and make process abort.
94 smash_stack_dummy_function(plen);
95 return 0;
96 }
97
98 #pragma clang diagnostic push
99 #pragma clang diagnostic ignored "-Winfinite-recursion"
100
101 void* global = 0; // So GCC doesn't optimize the tail recursion out of overflow_stack.
102
overflow_stack(void * p)103 noinline void overflow_stack(void* p) {
104 void* buf[1];
105 buf[0] = p;
106 global = buf;
107 overflow_stack(&buf);
108 }
109
110 #pragma clang diagnostic pop
111
thread_callback(void * raw_arg)112 noinline void* thread_callback(void* raw_arg) {
113 const char* arg = reinterpret_cast<const char*>(raw_arg);
114 return reinterpret_cast<void*>(static_cast<uintptr_t>(do_action(arg)));
115 }
116
do_action_on_thread(const char * arg)117 noinline int do_action_on_thread(const char* arg) {
118 pthread_t t;
119 pthread_create(&t, nullptr, thread_callback, const_cast<char*>(arg));
120 void* result = nullptr;
121 pthread_join(t, &result);
122 return reinterpret_cast<uintptr_t>(result);
123 }
124
crash_null()125 noinline int crash_null() {
126 int (*null_func)() = nullptr;
127 return null_func();
128 }
129
crash3(int a)130 noinline int crash3(int a) {
131 *reinterpret_cast<int*>(0xdead) = a;
132 return a*4;
133 }
134
crash2(int a)135 noinline int crash2(int a) {
136 a = crash3(a) + 2;
137 return a*3;
138 }
139
crash(int a)140 noinline int crash(int a) {
141 a = crash2(a) + 1;
142 return a*2;
143 }
144
145 #pragma clang diagnostic push
146 #pragma clang diagnostic ignored "-Wfree-nonheap-object"
147
abuse_heap()148 noinline void abuse_heap() {
149 char buf[16];
150 free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately.
151 }
152 #pragma clang diagnostic pop
153
leak()154 noinline void leak() {
155 while (true) {
156 void* mapping =
157 mmap(nullptr, getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
158 static_cast<volatile char*>(mapping)[0] = 'a';
159 }
160 }
161
sigsegv_non_null()162 noinline void sigsegv_non_null() {
163 int* a = (int *)(&do_action);
164 *a = 42;
165 }
166
fprintf_null()167 noinline void fprintf_null() {
168 FILE* sneaky_null = nullptr;
169 fprintf(sneaky_null, "oops");
170 }
171
readdir_null()172 noinline void readdir_null() {
173 DIR* sneaky_null = nullptr;
174 readdir(sneaky_null);
175 }
176
strlen_null()177 noinline int strlen_null() {
178 char* sneaky_null = nullptr;
179 return strlen(sneaky_null);
180 }
181
usage()182 static int usage() {
183 fprintf(stderr, "usage: %s KIND\n", getprogname());
184 fprintf(stderr, "\n");
185 fprintf(stderr, "where KIND is:\n");
186 fprintf(stderr, " smash-stack overwrite a -fstack-protector guard\n");
187 fprintf(stderr, " stack-overflow recurse until the stack overflows\n");
188 fprintf(stderr, " nostack crash with a NULL stack pointer\n");
189 fprintf(stderr, "\n");
190 fprintf(stderr, " heap-usage cause a libc abort by abusing a heap function\n");
191 fprintf(stderr, " call-null cause a crash by calling through a nullptr\n");
192 fprintf(stderr, " leak leak memory until we get OOM-killed\n");
193 fprintf(stderr, "\n");
194 fprintf(stderr, " abort call abort()\n");
195 fprintf(stderr, " abort_with_msg call abort() setting an abort message\n");
196 fprintf(stderr, " abort_with_null_msg call abort() setting a null abort message\n");
197 fprintf(stderr, " assert call assert() without a function\n");
198 fprintf(stderr, " assert2 call assert() with a function\n");
199 fprintf(stderr, " exit call exit(1)\n");
200 fprintf(stderr, "\n");
201 fprintf(stderr, " fortify fail a _FORTIFY_SOURCE check\n");
202 fprintf(stderr, " fdsan_file close a file descriptor that's owned by a FILE*\n");
203 fprintf(stderr, " fdsan_dir close a file descriptor that's owned by a DIR*\n");
204 fprintf(stderr, " seccomp fail a seccomp check\n");
205 #if defined(__LP64__)
206 fprintf(stderr, " xom read execute-only memory\n");
207 #endif
208 fprintf(stderr, "\n");
209 fprintf(stderr, " LOG_ALWAYS_FATAL call liblog LOG_ALWAYS_FATAL\n");
210 fprintf(stderr, " LOG_ALWAYS_FATAL_IF call liblog LOG_ALWAYS_FATAL_IF\n");
211 fprintf(stderr, " LOG-FATAL call libbase LOG(FATAL)\n");
212 fprintf(stderr, "\n");
213 fprintf(stderr, " SIGFPE cause a SIGFPE\n");
214 fprintf(stderr, " SIGILL cause a SIGILL\n");
215 fprintf(stderr, " SIGSEGV cause a SIGSEGV at address 0x0 (synonym: crash)\n");
216 fprintf(stderr, " SIGSEGV-non-null cause a SIGSEGV at a non-zero address\n");
217 fprintf(stderr, " SIGSEGV-unmapped mmap/munmap a region of memory and then attempt to access it\n");
218 fprintf(stderr, " SIGTRAP cause a SIGTRAP\n");
219 fprintf(stderr, "\n");
220 fprintf(stderr, " fprintf-NULL pass a null pointer to fprintf\n");
221 fprintf(stderr, " readdir-NULL pass a null pointer to readdir\n");
222 fprintf(stderr, " strlen-NULL pass a null pointer to strlen\n");
223 fprintf(stderr, " pthread_join-NULL pass a null pointer to pthread_join\n");
224 fprintf(stderr, "\n");
225 fprintf(stderr, " no_new_privs set PR_SET_NO_NEW_PRIVS and then abort\n");
226 fprintf(stderr, "\n");
227 #if defined(__arm__)
228 fprintf(stderr, "Also, since this is an arm32 binary:\n");
229 fprintf(stderr, " kuser_helper_version call kuser_helper_version\n");
230 fprintf(stderr, " kuser_get_tls call kuser_get_tls\n");
231 fprintf(stderr, " kuser_cmpxchg call kuser_cmpxchg\n");
232 fprintf(stderr, " kuser_memory_barrier call kuser_memory_barrier\n");
233 fprintf(stderr, " kuser_cmpxchg64 call kuser_cmpxchg64\n");
234 #endif
235 #if defined(__aarch64__)
236 fprintf(stderr, "Also, since this is an arm64 binary:\n");
237 fprintf(stderr, " bti fail a branch target identification (BTI) check\n");
238 fprintf(stderr, " pac fail a pointer authentication (PAC) check\n");
239 #endif
240 fprintf(stderr, "\n");
241 fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n");
242 fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n");
243 fprintf(stderr, "all available file descriptors before crashing.\n");
244 fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n");
245
246 return EXIT_FAILURE;
247 }
248
CheckCpuFeature(const std::string & name)249 [[maybe_unused]] static void CheckCpuFeature(const std::string& name) {
250 std::string cpuinfo;
251 if (!android::base::ReadFileToString("/proc/cpuinfo", &cpuinfo)) {
252 error(1, errno, "couldn't read /proc/cpuinfo");
253 }
254 std::vector<std::string> lines = android::base::Split(cpuinfo, "\n");
255 for (std::string_view line : lines) {
256 if (!android::base::ConsumePrefix(&line, "Features\t:")) continue;
257 std::vector<std::string> features = android::base::Split(std::string(line), " ");
258 if (std::find(features.begin(), features.end(), name) == features.end()) {
259 error(1, 0, "/proc/cpuinfo does not report feature '%s'", name.c_str());
260 }
261 }
262 }
263
do_action(const char * arg)264 noinline int do_action(const char* arg) {
265 // Prefixes.
266 if (!strncmp(arg, "wait-", strlen("wait-"))) {
267 char buf[1];
268 UNUSED(TEMP_FAILURE_RETRY(read(STDIN_FILENO, buf, sizeof(buf))));
269 return do_action(arg + strlen("wait-"));
270 } else if (!strncmp(arg, "exhaustfd-", strlen("exhaustfd-"))) {
271 errno = 0;
272 while (errno != EMFILE) {
273 open("/dev/null", O_RDONLY);
274 }
275 return do_action(arg + strlen("exhaustfd-"));
276 } else if (!strncmp(arg, "thread-", strlen("thread-"))) {
277 return do_action_on_thread(arg + strlen("thread-"));
278 }
279
280 // Actions.
281 if (!strcasecmp(arg, "SIGSEGV-non-null")) {
282 sigsegv_non_null();
283 } else if (!strcasecmp(arg, "smash-stack")) {
284 volatile int len = 128;
285 return smash_stack(&len);
286 } else if (!strcasecmp(arg, "stack-overflow")) {
287 overflow_stack(nullptr);
288 } else if (!strcasecmp(arg, "nostack")) {
289 crash_no_stack();
290 } else if (!strcasecmp(arg, "exit")) {
291 exit(1);
292 } else if (!strcasecmp(arg, "call-null")) {
293 return crash_null();
294 } else if (!strcasecmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) {
295 return crash(42);
296 } else if (!strcasecmp(arg, "abort")) {
297 maybe_abort();
298 } else if (!strcasecmp(arg, "abort_with_msg")) {
299 android_set_abort_message("Aborting due to crasher");
300 maybe_abort();
301 } else if (!strcasecmp(arg, "abort_with_null")) {
302 android_set_abort_message(nullptr);
303 maybe_abort();
304 } else if (!strcasecmp(arg, "assert")) {
305 __assert("some_file.c", 123, "false");
306 } else if (!strcasecmp(arg, "assert2")) {
307 __assert2("some_file.c", 123, "some_function", "false");
308 #if !defined(__clang_analyzer__)
309 } else if (!strcasecmp(arg, "fortify")) {
310 // FORTIFY is disabled when running clang-tidy and other tools, so this
311 // shouldn't depend on internal implementation details of it.
312 char buf[10];
313 __read_chk(-1, buf, 32, 10);
314 while (true) pause();
315 #endif
316 } else if (!strcasecmp(arg, "fdsan_file")) {
317 FILE* f = fopen("/dev/null", "r");
318 close(fileno(f));
319 } else if (!strcasecmp(arg, "fdsan_dir")) {
320 DIR* d = opendir("/dev/");
321 close(dirfd(d));
322 } else if (!strcasecmp(arg, "LOG(FATAL)")) {
323 LOG(FATAL) << "hello " << 123;
324 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL")) {
325 LOG_ALWAYS_FATAL("hello %s", "world");
326 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL_IF")) {
327 LOG_ALWAYS_FATAL_IF(true, "hello %s", "world");
328 } else if (!strcasecmp(arg, "SIGFPE")) {
329 raise(SIGFPE);
330 return EXIT_SUCCESS;
331 } else if (!strcasecmp(arg, "SIGILL")) {
332 #if defined(__aarch64__)
333 __asm__ volatile(".word 0\n");
334 #elif defined(__arm__)
335 __asm__ volatile(".word 0xe7f0def0\n");
336 #elif defined(__i386__) || defined(__x86_64__)
337 __asm__ volatile("ud2\n");
338 #elif defined(__riscv)
339 __asm__ volatile("unimp\n");
340 #else
341 #error
342 #endif
343 } else if (!strcasecmp(arg, "SIGTRAP")) {
344 raise(SIGTRAP);
345 return EXIT_SUCCESS;
346 } else if (!strcasecmp(arg, "fprintf-NULL")) {
347 fprintf_null();
348 } else if (!strcasecmp(arg, "readdir-NULL")) {
349 readdir_null();
350 } else if (!strcasecmp(arg, "strlen-NULL")) {
351 return strlen_null();
352 } else if (!strcasecmp(arg, "pthread_join-NULL")) {
353 return pthread_join(0, nullptr);
354 } else if (!strcasecmp(arg, "heap-usage")) {
355 abuse_heap();
356 } else if (!strcasecmp(arg, "leak")) {
357 leak();
358 } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) {
359 char* map = reinterpret_cast<char*>(
360 mmap(nullptr, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0));
361 munmap(map, sizeof(int));
362 map[0] = '8';
363 } else if (!strcasecmp(arg, "seccomp")) {
364 set_system_seccomp_filter();
365 syscall(99999);
366 #if defined(__LP64__)
367 } else if (!strcasecmp(arg, "xom")) {
368 // Try to read part of our code, which will fail if XOM is active.
369 printf("*%lx = %lx\n", reinterpret_cast<long>(usage), *reinterpret_cast<long*>(usage));
370 #endif
371 #if defined(__arm__)
372 } else if (!strcasecmp(arg, "kuser_helper_version")) {
373 return __kuser_helper_version;
374 } else if (!strcasecmp(arg, "kuser_get_tls")) {
375 return !__kuser_get_tls();
376 } else if (!strcasecmp(arg, "kuser_cmpxchg")) {
377 return __kuser_cmpxchg(0, 0, 0);
378 } else if (!strcasecmp(arg, "kuser_memory_barrier")) {
379 __kuser_dmb();
380 } else if (!strcasecmp(arg, "kuser_cmpxchg64")) {
381 return __kuser_cmpxchg64(0, 0, 0);
382 #endif
383 #if defined(__aarch64__)
384 } else if (!strcasecmp(arg, "bti")) {
385 CheckCpuFeature("bti");
386 crash_bti();
387 } else if (!strcasecmp(arg, "pac")) {
388 CheckCpuFeature("paca");
389 crash_pac();
390 #endif
391 } else if (!strcasecmp(arg, "no_new_privs")) {
392 if (prctl(PR_SET_NO_NEW_PRIVS, 1) != 0) {
393 fprintf(stderr, "prctl(PR_SET_NO_NEW_PRIVS, 1) failed: %s\n", strerror(errno));
394 return EXIT_SUCCESS;
395 }
396 abort();
397 } else {
398 return usage();
399 }
400
401 fprintf(stderr, "%s: exiting normally!\n", getprogname());
402 return EXIT_SUCCESS;
403 }
404
main(int argc,char ** argv)405 int main(int argc, char** argv) {
406 #if defined(STATIC_CRASHER)
407 debuggerd_callbacks_t callbacks = {
408 .get_process_info = []() {
409 static struct {
410 size_t size;
411 char msg[32];
412 } msg;
413
414 msg.size = strlen("dummy abort message");
415 memcpy(msg.msg, "dummy abort message", strlen("dummy abort message"));
416 return debugger_process_info{
417 .abort_msg = reinterpret_cast<void*>(&msg),
418 };
419 },
420 .post_dump = nullptr
421 };
422 debuggerd_init(&callbacks);
423 #endif
424
425 if (argc == 1) crash1();
426 else if (argc == 2) return do_action(argv[1]);
427
428 return usage();
429 }
430
431 };
432