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 65 noinline void maybe_abort() { 66 if (time(0) != 42) { 67 abort(); 68 } 69 } 70 71 char* smash_stack_dummy_buf; 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. 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 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 103 104 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 } 108 109 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 } 116 117 noinline int crash3(int a) { 118 *reinterpret_cast<int*>(0xdead) = a; 119 return a*4; 120 } 121 122 noinline int crash2(int a) { 123 a = crash3(a) + 2; 124 return a*3; 125 } 126 127 noinline int crash(int a) { 128 a = crash2(a) + 1; 129 return a*2; 130 } 131 132 noinline void abuse_heap() { 133 char buf[16]; 134 free(buf); // GCC is smart enough to warn about this, but we're doing it deliberately. 135 } 136 137 noinline void leak() { 138 while (true) { 139 void* mapping = 140 mmap(nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 141 static_cast<volatile char*>(mapping)[0] = 'a'; 142 } 143 } 144 145 noinline void sigsegv_non_null() { 146 int* a = (int *)(&do_action); 147 *a = 42; 148 } 149 150 noinline void fprintf_null() { 151 fprintf(nullptr, "oops"); 152 } 153 154 noinline void readdir_null() { 155 readdir(nullptr); 156 } 157 158 noinline int strlen_null() { 159 char* sneaky_null = nullptr; 160 return strlen(sneaky_null); 161 } 162 163 static int usage() { 164 fprintf(stderr, "usage: %s KIND\n", getprogname()); 165 fprintf(stderr, "\n"); 166 fprintf(stderr, "where KIND is:\n"); 167 fprintf(stderr, " smash-stack overwrite a -fstack-protector guard\n"); 168 fprintf(stderr, " stack-overflow recurse until the stack overflows\n"); 169 fprintf(stderr, " nostack crash with a NULL stack pointer\n"); 170 fprintf(stderr, "\n"); 171 fprintf(stderr, " heap-usage cause a libc abort by abusing a heap function\n"); 172 fprintf(stderr, " leak leak memory until we get OOM-killed\n"); 173 fprintf(stderr, "\n"); 174 fprintf(stderr, " abort call abort()\n"); 175 fprintf(stderr, " assert call assert() without a function\n"); 176 fprintf(stderr, " assert2 call assert() with a function\n"); 177 fprintf(stderr, " exit call exit(1)\n"); 178 fprintf(stderr, "\n"); 179 fprintf(stderr, " fortify fail a _FORTIFY_SOURCE check\n"); 180 fprintf(stderr, " seccomp fail a seccomp check\n"); 181 #if defined(__arm__) 182 fprintf(stderr, " kuser_helper_version call kuser_helper_version\n"); 183 fprintf(stderr, " kuser_get_tls call kuser_get_tls\n"); 184 fprintf(stderr, " kuser_cmpxchg call kuser_cmpxchg\n"); 185 fprintf(stderr, " kuser_memory_barrier call kuser_memory_barrier\n"); 186 fprintf(stderr, " kuser_cmpxchg64 call kuser_cmpxchg64\n"); 187 #endif 188 fprintf(stderr, "\n"); 189 fprintf(stderr, " LOG_ALWAYS_FATAL call liblog LOG_ALWAYS_FATAL\n"); 190 fprintf(stderr, " LOG_ALWAYS_FATAL_IF call liblog LOG_ALWAYS_FATAL_IF\n"); 191 fprintf(stderr, " LOG-FATAL call libbase LOG(FATAL)\n"); 192 fprintf(stderr, "\n"); 193 fprintf(stderr, " SIGFPE cause a SIGFPE\n"); 194 fprintf(stderr, " SIGSEGV cause a SIGSEGV at address 0x0 (synonym: crash)\n"); 195 fprintf(stderr, " SIGSEGV-non-null cause a SIGSEGV at a non-zero address\n"); 196 fprintf(stderr, " SIGSEGV-unmapped mmap/munmap a region of memory and then attempt to access it\n"); 197 fprintf(stderr, " SIGTRAP cause a SIGTRAP\n"); 198 fprintf(stderr, "\n"); 199 fprintf(stderr, " fprintf-NULL pass a null pointer to fprintf\n"); 200 fprintf(stderr, " readdir-NULL pass a null pointer to readdir\n"); 201 fprintf(stderr, " strlen-NULL pass a null pointer to strlen\n"); 202 fprintf(stderr, " pthread_join-NULL pass a null pointer to pthread_join\n"); 203 fprintf(stderr, "\n"); 204 fprintf(stderr, " no_new_privs set PR_SET_NO_NEW_PRIVS and then abort\n"); 205 fprintf(stderr, "\n"); 206 fprintf(stderr, "prefix any of the above with 'thread-' to run on a new thread\n"); 207 fprintf(stderr, "prefix any of the above with 'exhaustfd-' to exhaust\n"); 208 fprintf(stderr, "all available file descriptors before crashing.\n"); 209 fprintf(stderr, "prefix any of the above with 'wait-' to wait until input is received on stdin\n"); 210 211 return EXIT_FAILURE; 212 } 213 214 noinline int do_action(const char* arg) { 215 // Prefixes. 216 if (!strncmp(arg, "wait-", strlen("wait-"))) { 217 char buf[1]; 218 TEMP_FAILURE_RETRY(read(STDIN_FILENO, buf, sizeof(buf))); 219 return do_action(arg + strlen("wait-")); 220 } else if (!strncmp(arg, "exhaustfd-", strlen("exhaustfd-"))) { 221 errno = 0; 222 while (errno != EMFILE) { 223 open("/dev/null", O_RDONLY); 224 } 225 return do_action(arg + strlen("exhaustfd-")); 226 } else if (!strncmp(arg, "thread-", strlen("thread-"))) { 227 return do_action_on_thread(arg + strlen("thread-")); 228 } 229 230 // Actions. 231 if (!strcasecmp(arg, "SIGSEGV-non-null")) { 232 sigsegv_non_null(); 233 } else if (!strcasecmp(arg, "smash-stack")) { 234 volatile int len = 128; 235 return smash_stack(&len); 236 } else if (!strcasecmp(arg, "stack-overflow")) { 237 overflow_stack(nullptr); 238 } else if (!strcasecmp(arg, "nostack")) { 239 crashnostack(); 240 } else if (!strcasecmp(arg, "exit")) { 241 exit(1); 242 } else if (!strcasecmp(arg, "crash") || !strcmp(arg, "SIGSEGV")) { 243 return crash(42); 244 } else if (!strcasecmp(arg, "abort")) { 245 maybe_abort(); 246 } else if (!strcasecmp(arg, "assert")) { 247 __assert("some_file.c", 123, "false"); 248 } else if (!strcasecmp(arg, "assert2")) { 249 __assert2("some_file.c", 123, "some_function", "false"); 250 } else if (!strcasecmp(arg, "fortify")) { 251 char buf[10]; 252 __read_chk(-1, buf, 32, 10); 253 while (true) pause(); 254 } else if (!strcasecmp(arg, "LOG(FATAL)")) { 255 LOG(FATAL) << "hello " << 123; 256 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL")) { 257 LOG_ALWAYS_FATAL("hello %s", "world"); 258 } else if (!strcasecmp(arg, "LOG_ALWAYS_FATAL_IF")) { 259 LOG_ALWAYS_FATAL_IF(true, "hello %s", "world"); 260 } else if (!strcasecmp(arg, "SIGFPE")) { 261 raise(SIGFPE); 262 return EXIT_SUCCESS; 263 } else if (!strcasecmp(arg, "SIGTRAP")) { 264 raise(SIGTRAP); 265 return EXIT_SUCCESS; 266 } else if (!strcasecmp(arg, "fprintf-NULL")) { 267 fprintf_null(); 268 } else if (!strcasecmp(arg, "readdir-NULL")) { 269 readdir_null(); 270 } else if (!strcasecmp(arg, "strlen-NULL")) { 271 return strlen_null(); 272 } else if (!strcasecmp(arg, "pthread_join-NULL")) { 273 return pthread_join(0, nullptr); 274 } else if (!strcasecmp(arg, "heap-usage")) { 275 abuse_heap(); 276 } else if (!strcasecmp(arg, "leak")) { 277 leak(); 278 } else if (!strcasecmp(arg, "SIGSEGV-unmapped")) { 279 char* map = reinterpret_cast<char*>(mmap(nullptr, sizeof(int), PROT_READ | PROT_WRITE, 280 MAP_SHARED | MAP_ANONYMOUS, -1, 0)); 281 munmap(map, sizeof(int)); 282 map[0] = '8'; 283 } else if (!strcasecmp(arg, "seccomp")) { 284 set_seccomp_filter(); 285 syscall(99999); 286 #if defined(__arm__) 287 } else if (!strcasecmp(arg, "kuser_helper_version")) { 288 return __kuser_helper_version; 289 } else if (!strcasecmp(arg, "kuser_get_tls")) { 290 return !__kuser_get_tls(); 291 } else if (!strcasecmp(arg, "kuser_cmpxchg")) { 292 return __kuser_cmpxchg(0, 0, 0); 293 } else if (!strcasecmp(arg, "kuser_memory_barrier")) { 294 __kuser_dmb(); 295 } else if (!strcasecmp(arg, "kuser_cmpxchg64")) { 296 return __kuser_cmpxchg64(0, 0, 0); 297 #endif 298 } else if (!strcasecmp(arg, "no_new_privs")) { 299 if (prctl(PR_SET_NO_NEW_PRIVS, 1) != 0) { 300 fprintf(stderr, "prctl(PR_SET_NO_NEW_PRIVS, 1) failed: %s\n", strerror(errno)); 301 return EXIT_SUCCESS; 302 } 303 abort(); 304 } else { 305 return usage(); 306 } 307 308 fprintf(stderr, "%s: exiting normally!\n", getprogname()); 309 return EXIT_SUCCESS; 310 } 311 312 int main(int argc, char** argv) { 313 #if defined(STATIC_CRASHER) 314 debuggerd_callbacks_t callbacks = { 315 .get_abort_message = []() { 316 static struct { 317 size_t size; 318 char msg[32]; 319 } msg; 320 321 msg.size = strlen("dummy abort message"); 322 memcpy(msg.msg, "dummy abort message", strlen("dummy abort message")); 323 return reinterpret_cast<abort_msg_t*>(&msg); 324 }, 325 .post_dump = nullptr 326 }; 327 debuggerd_init(&callbacks); 328 #endif 329 330 if (argc == 1) crash1(); 331 else if (argc == 2) return do_action(argv[1]); 332 333 return usage(); 334 } 335 336 }; 337
