com_android_internal_os_Zygote.cpp revision 160992da04cab56a92cd425adc249c52b040f93d
1/* 2 * Copyright (C) 2008 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_runtime/AndroidRuntime.h" 18 19// sys/mount.h has to come before linux/fs.h due to redefinition of MS_RDONLY, MS_BIND, etc 20#include <sys/mount.h> 21#include <linux/fs.h> 22 23#include <grp.h> 24#include <paths.h> 25#include <signal.h> 26#include <stdlib.h> 27#include <sys/resource.h> 28#include <sys/types.h> 29#include <sys/stat.h> 30#include <sys/wait.h> 31#include <unistd.h> 32#include <fcntl.h> 33 34#include "cutils/fs.h" 35#include "cutils/multiuser.h" 36#include "cutils/sched_policy.h" 37#include "utils/String8.h" 38#include "JNIHelp.h" 39#include "ScopedLocalRef.h" 40#include "ScopedPrimitiveArray.h" 41#include "ScopedUtfChars.h" 42 43#if defined(HAVE_PRCTL) 44#include <sys/prctl.h> 45#endif 46 47#include <selinux/android.h> 48 49#if defined(__linux__) 50#include <sys/personality.h> 51#include <sys/utsname.h> 52#if defined(HAVE_ANDROID_OS) 53#include <sys/capability.h> 54#endif 55#endif 56 57namespace { 58 59using android::String8; 60 61static pid_t gSystemServerPid = 0; 62 63static const char kZygoteClassName[] = "com/android/internal/os/Zygote"; 64static jclass gZygoteClass; 65static jmethodID gCallPostForkChildHooks; 66 67// Must match values in com.android.internal.os.Zygote. 68enum MountExternalKind { 69 MOUNT_EXTERNAL_NONE = 0, 70 MOUNT_EXTERNAL_SINGLEUSER = 1, 71 MOUNT_EXTERNAL_MULTIUSER = 2, 72 MOUNT_EXTERNAL_MULTIUSER_ALL = 3, 73}; 74 75static void RuntimeAbort(JNIEnv* env) { 76 env->FatalError("RuntimeAbort"); 77} 78 79// This signal handler is for zygote mode, since the zygote must reap its children 80static void SigChldHandler(int /*signal_number*/) { 81 pid_t pid; 82 int status; 83 84 while ((pid = waitpid(-1, &status, WNOHANG)) > 0) { 85 // Log process-death status that we care about. In general it is 86 // not safe to call LOG(...) from a signal handler because of 87 // possible reentrancy. However, we know a priori that the 88 // current implementation of LOG() is safe to call from a SIGCHLD 89 // handler in the zygote process. If the LOG() implementation 90 // changes its locking strategy or its use of syscalls within the 91 // lazy-init critical section, its use here may become unsafe. 92 if (WIFEXITED(status)) { 93 if (WEXITSTATUS(status)) { 94 ALOGI("Process %d exited cleanly (%d)", pid, WEXITSTATUS(status)); 95 } 96 } else if (WIFSIGNALED(status)) { 97 if (WTERMSIG(status) != SIGKILL) { 98 ALOGI("Process %d exited due to signal (%d)", pid, WTERMSIG(status)); 99 } 100#ifdef WCOREDUMP 101 if (WCOREDUMP(status)) { 102 ALOGI("Process %d dumped core.", pid); 103 } 104#endif /* ifdef WCOREDUMP */ 105 } 106 107 // If the just-crashed process is the system_server, bring down zygote 108 // so that it is restarted by init and system server will be restarted 109 // from there. 110 if (pid == gSystemServerPid) { 111 ALOGE("Exit zygote because system server (%d) has terminated"); 112 kill(getpid(), SIGKILL); 113 } 114 } 115 116 // Note that we shouldn't consider ECHILD an error because 117 // the secondary zygote might have no children left to wait for. 118 if (pid < 0 && errno != ECHILD) { 119 ALOGW("Zygote SIGCHLD error in waitpid: %s", strerror(errno)); 120 } 121} 122 123// Configures the SIGCHLD handler for the zygote process. This is configured 124// very late, because earlier in the runtime we may fork() and exec() 125// other processes, and we want to waitpid() for those rather than 126// have them be harvested immediately. 127// 128// This ends up being called repeatedly before each fork(), but there's 129// no real harm in that. 130static void SetSigChldHandler() { 131 struct sigaction sa; 132 memset(&sa, 0, sizeof(sa)); 133 sa.sa_handler = SigChldHandler; 134 135 int err = sigaction(SIGCHLD, &sa, NULL); 136 if (err < 0) { 137 ALOGW("Error setting SIGCHLD handler: %d", errno); 138 } 139} 140 141// Sets the SIGCHLD handler back to default behavior in zygote children. 142static void UnsetSigChldHandler() { 143 struct sigaction sa; 144 memset(&sa, 0, sizeof(sa)); 145 sa.sa_handler = SIG_DFL; 146 147 int err = sigaction(SIGCHLD, &sa, NULL); 148 if (err < 0) { 149 ALOGW("Error unsetting SIGCHLD handler: %d", errno); 150 } 151} 152 153// Calls POSIX setgroups() using the int[] object as an argument. 154// A NULL argument is tolerated. 155static void SetGids(JNIEnv* env, jintArray javaGids) { 156 if (javaGids == NULL) { 157 return; 158 } 159 160 ScopedIntArrayRO gids(env, javaGids); 161 if (gids.get() == NULL) { 162 RuntimeAbort(env); 163 } 164 int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0])); 165 if (rc == -1) { 166 ALOGE("setgroups failed"); 167 RuntimeAbort(env); 168 } 169} 170 171// Sets the resource limits via setrlimit(2) for the values in the 172// two-dimensional array of integers that's passed in. The second dimension 173// contains a tuple of length 3: (resource, rlim_cur, rlim_max). NULL is 174// treated as an empty array. 175static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) { 176 if (javaRlimits == NULL) { 177 return; 178 } 179 180 rlimit rlim; 181 memset(&rlim, 0, sizeof(rlim)); 182 183 for (int i = 0; i < env->GetArrayLength(javaRlimits); ++i) { 184 ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i)); 185 ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get())); 186 if (javaRlimit.size() != 3) { 187 ALOGE("rlimits array must have a second dimension of size 3"); 188 RuntimeAbort(env); 189 } 190 191 rlim.rlim_cur = javaRlimit[1]; 192 rlim.rlim_max = javaRlimit[2]; 193 194 int rc = setrlimit(javaRlimit[0], &rlim); 195 if (rc == -1) { 196 ALOGE("setrlimit(%d, {%d, %d}) failed", javaRlimit[0], rlim.rlim_cur, rlim.rlim_max); 197 RuntimeAbort(env); 198 } 199 } 200} 201 202#if defined(HAVE_ANDROID_OS) 203 204// The debug malloc library needs to know whether it's the zygote or a child. 205extern "C" int gMallocLeakZygoteChild; 206 207static void EnableKeepCapabilities(JNIEnv* env) { 208 int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0); 209 if (rc == -1) { 210 ALOGE("prctl(PR_SET_KEEPCAPS) failed"); 211 RuntimeAbort(env); 212 } 213} 214 215static void DropCapabilitiesBoundingSet(JNIEnv* env) { 216 for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) { 217 int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0); 218 if (rc == -1) { 219 if (errno == EINVAL) { 220 ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify " 221 "your kernel is compiled with file capabilities support"); 222 } else { 223 ALOGE("prctl(PR_CAPBSET_DROP) failed"); 224 RuntimeAbort(env); 225 } 226 } 227 } 228} 229 230static void SetCapabilities(JNIEnv* env, int64_t permitted, int64_t effective) { 231 __user_cap_header_struct capheader; 232 memset(&capheader, 0, sizeof(capheader)); 233 capheader.version = _LINUX_CAPABILITY_VERSION_3; 234 capheader.pid = 0; 235 236 __user_cap_data_struct capdata[2]; 237 memset(&capdata, 0, sizeof(capdata)); 238 capdata[0].effective = effective; 239 capdata[1].effective = effective >> 32; 240 capdata[0].permitted = permitted; 241 capdata[1].permitted = permitted >> 32; 242 243 if (capset(&capheader, &capdata[0]) == -1) { 244 ALOGE("capset(%lld, %lld) failed", permitted, effective); 245 RuntimeAbort(env); 246 } 247} 248 249static void SetSchedulerPolicy(JNIEnv* env) { 250 errno = -set_sched_policy(0, SP_DEFAULT); 251 if (errno != 0) { 252 ALOGE("set_sched_policy(0, SP_DEFAULT) failed"); 253 RuntimeAbort(env); 254 } 255} 256 257#else 258 259static int gMallocLeakZygoteChild = 0; 260 261static void EnableKeepCapabilities(JNIEnv*) {} 262static void DropCapabilitiesBoundingSet(JNIEnv*) {} 263static void SetCapabilities(JNIEnv*, int64_t, int64_t) {} 264static void SetSchedulerPolicy(JNIEnv*) {} 265 266#endif 267 268// Create a private mount namespace and bind mount appropriate emulated 269// storage for the given user. 270static bool MountEmulatedStorage(uid_t uid, jint mount_mode) { 271 if (mount_mode == MOUNT_EXTERNAL_NONE) { 272 return true; 273 } 274 275 // See storage config details at http://source.android.com/tech/storage/ 276 userid_t user_id = multiuser_get_user_id(uid); 277 278 // Create a second private mount namespace for our process 279 if (unshare(CLONE_NEWNS) == -1) { 280 ALOGW("Failed to unshare(): %d", errno); 281 return false; 282 } 283 284 // Create bind mounts to expose external storage 285 if (mount_mode == MOUNT_EXTERNAL_MULTIUSER || mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) { 286 // These paths must already be created by init.rc 287 const char* source = getenv("EMULATED_STORAGE_SOURCE"); 288 const char* target = getenv("EMULATED_STORAGE_TARGET"); 289 const char* legacy = getenv("EXTERNAL_STORAGE"); 290 if (source == NULL || target == NULL || legacy == NULL) { 291 ALOGW("Storage environment undefined; unable to provide external storage"); 292 return false; 293 } 294 295 // Prepare source paths 296 297 // /mnt/shell/emulated/0 298 const String8 source_user(String8::format("%s/%d", source, user_id)); 299 // /storage/emulated/0 300 const String8 target_user(String8::format("%s/%d", target, user_id)); 301 302 if (fs_prepare_dir(source_user.string(), 0000, 0, 0) == -1 303 || fs_prepare_dir(target_user.string(), 0000, 0, 0) == -1) { 304 return false; 305 } 306 307 if (mount_mode == MOUNT_EXTERNAL_MULTIUSER_ALL) { 308 // Mount entire external storage tree for all users 309 if (TEMP_FAILURE_RETRY(mount(source, target, NULL, MS_BIND, NULL)) == -1) { 310 ALOGW("Failed to mount %s to %s :%d", source, target, errno); 311 return false; 312 } 313 } else { 314 // Only mount user-specific external storage 315 if (TEMP_FAILURE_RETRY( 316 mount(source_user.string(), target_user.string(), NULL, MS_BIND, NULL)) == -1) { 317 ALOGW("Failed to mount %s to %s: %d", source_user.string(), target_user.string(), errno); 318 return false; 319 } 320 } 321 322 if (fs_prepare_dir(legacy, 0000, 0, 0) == -1) { 323 return false; 324 } 325 326 // Finally, mount user-specific path into place for legacy users 327 if (TEMP_FAILURE_RETRY( 328 mount(target_user.string(), legacy, NULL, MS_BIND | MS_REC, NULL)) == -1) { 329 ALOGW("Failed to mount %s to %s: %d", target_user.string(), legacy, errno); 330 return false; 331 } 332 } else { 333 ALOGW("Mount mode %d unsupported", mount_mode); 334 return false; 335 } 336 337 return true; 338} 339 340#if defined(__linux__) 341static bool NeedsNoRandomizeWorkaround() { 342#if !defined(__arm__) 343 return false; 344#else 345 int major; 346 int minor; 347 struct utsname uts; 348 if (uname(&uts) == -1) { 349 return false; 350 } 351 352 if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) { 353 return false; 354 } 355 356 // Kernels before 3.4.* need the workaround. 357 return (major < 3) || ((major == 3) && (minor < 4)); 358#endif 359} 360#endif 361 362// Utility to close down the Zygote socket file descriptors while 363// the child is still running as root with Zygote's privileges. Each 364// descriptor (if any) is closed via dup2(), replacing it with a valid 365// (open) descriptor to /dev/null. 366 367static void DetachDescriptors(JNIEnv* env, jintArray fdsToClose) { 368 if (!fdsToClose) { 369 return; 370 } 371 jsize count = env->GetArrayLength(fdsToClose); 372 jint *ar = env->GetIntArrayElements(fdsToClose, 0); 373 if (!ar) { 374 ALOGE("Bad fd array"); 375 RuntimeAbort(env); 376 } 377 jsize i; 378 int devnull; 379 for (i = 0; i < count; i++) { 380 devnull = open("/dev/null", O_RDWR); 381 if (devnull < 0) { 382 ALOGE("Failed to open /dev/null"); 383 RuntimeAbort(env); 384 continue; 385 } 386 ALOGV("Switching descriptor %d to /dev/null: %d", ar[i], errno); 387 if (dup2(devnull, ar[i]) < 0) { 388 ALOGE("Failed dup2() on descriptor %d", ar[i]); 389 RuntimeAbort(env); 390 } 391 close(devnull); 392 } 393} 394 395void SetThreadName(const char* thread_name) { 396 bool hasAt = false; 397 bool hasDot = false; 398 const char* s = thread_name; 399 while (*s) { 400 if (*s == '.') { 401 hasDot = true; 402 } else if (*s == '@') { 403 hasAt = true; 404 } 405 s++; 406 } 407 const int len = s - thread_name; 408 if (len < 15 || hasAt || !hasDot) { 409 s = thread_name; 410 } else { 411 s = thread_name + len - 15; 412 } 413 // pthread_setname_np fails rather than truncating long strings. 414 char buf[16]; // MAX_TASK_COMM_LEN=16 is hard-coded into bionic 415 strlcpy(buf, s, sizeof(buf)-1); 416 errno = pthread_setname_np(pthread_self(), buf); 417 if (errno != 0) { 418 ALOGW("Unable to set the name of current thread to '%s'", buf); 419 } 420} 421 422// Utility routine to fork zygote and specialize the child process. 423static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids, 424 jint debug_flags, jobjectArray javaRlimits, 425 jlong permittedCapabilities, jlong effectiveCapabilities, 426 jint mount_external, 427 jstring java_se_info, jstring java_se_name, 428 bool is_system_server, jintArray fdsToClose) { 429 SetSigChldHandler(); 430 431 pid_t pid = fork(); 432 433 if (pid == 0) { 434 // The child process. 435 gMallocLeakZygoteChild = 1; 436 437 // Clean up any descriptors which must be closed immediately 438 DetachDescriptors(env, fdsToClose); 439 440 // Keep capabilities across UID change, unless we're staying root. 441 if (uid != 0) { 442 EnableKeepCapabilities(env); 443 } 444 445 DropCapabilitiesBoundingSet(env); 446 447 if (!MountEmulatedStorage(uid, mount_external)) { 448 ALOGW("Failed to mount emulated storage: %d", errno); 449 if (errno == ENOTCONN || errno == EROFS) { 450 // When device is actively encrypting, we get ENOTCONN here 451 // since FUSE was mounted before the framework restarted. 452 // When encrypted device is booting, we get EROFS since 453 // FUSE hasn't been created yet by init. 454 // In either case, continue without external storage. 455 } else { 456 ALOGE("Cannot continue without emulated storage"); 457 RuntimeAbort(env); 458 } 459 } 460 461 SetGids(env, javaGids); 462 463 SetRLimits(env, javaRlimits); 464 465 int rc = setresgid(gid, gid, gid); 466 if (rc == -1) { 467 ALOGE("setresgid(%d) failed", gid); 468 RuntimeAbort(env); 469 } 470 471 rc = setresuid(uid, uid, uid); 472 if (rc == -1) { 473 ALOGE("setresuid(%d) failed", uid); 474 RuntimeAbort(env); 475 } 476 477#if defined(__linux__) 478 if (NeedsNoRandomizeWorkaround()) { 479 // Work around ARM kernel ASLR lossage (http://b/5817320). 480 int old_personality = personality(0xffffffff); 481 int new_personality = personality(old_personality | ADDR_NO_RANDOMIZE); 482 if (new_personality == -1) { 483 ALOGW("personality(%d) failed", new_personality); 484 } 485 } 486#endif 487 488 SetCapabilities(env, permittedCapabilities, effectiveCapabilities); 489 490 SetSchedulerPolicy(env); 491 492#if defined(HAVE_ANDROID_OS) 493 { // NOLINT(whitespace/braces) 494 const char* se_info_c_str = NULL; 495 ScopedUtfChars* se_info = NULL; 496 if (java_se_info != NULL) { 497 se_info = new ScopedUtfChars(env, java_se_info); 498 se_info_c_str = se_info->c_str(); 499 if (se_info_c_str == NULL) { 500 ALOGE("se_info_c_str == NULL"); 501 RuntimeAbort(env); 502 } 503 } 504 const char* se_name_c_str = NULL; 505 ScopedUtfChars* se_name = NULL; 506 if (java_se_name != NULL) { 507 se_name = new ScopedUtfChars(env, java_se_name); 508 se_name_c_str = se_name->c_str(); 509 if (se_name_c_str == NULL) { 510 ALOGE("se_name_c_str == NULL"); 511 RuntimeAbort(env); 512 } 513 } 514 rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str); 515 if (rc == -1) { 516 ALOGE("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed", uid, 517 is_system_server, se_info_c_str, se_name_c_str); 518 RuntimeAbort(env); 519 } 520 521 // Make it easier to debug audit logs by setting the main thread's name to the 522 // nice name rather than "app_process". 523 if (se_info_c_str == NULL && is_system_server) { 524 se_name_c_str = "system_server"; 525 } 526 if (se_info_c_str != NULL) { 527 SetThreadName(se_name_c_str); 528 } 529 530 delete se_info; 531 delete se_name; 532 } 533#else 534 UNUSED(is_system_server); 535 UNUSED(java_se_info); 536 UNUSED(java_se_name); 537#endif 538 539 UnsetSigChldHandler(); 540 541 env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, debug_flags); 542 if (env->ExceptionCheck()) { 543 ALOGE("Error calling post fork hooks."); 544 RuntimeAbort(env); 545 } 546 } else if (pid > 0) { 547 // the parent process 548 } 549 return pid; 550} 551} // anonymous namespace 552 553namespace android { 554 555static jint com_android_internal_os_Zygote_nativeForkAndSpecialize( 556 JNIEnv* env, jclass, jint uid, jint gid, jintArray gids, 557 jint debug_flags, jobjectArray rlimits, 558 jint mount_external, jstring se_info, jstring se_name, 559 jintArray fdsToClose) { 560 return ForkAndSpecializeCommon(env, uid, gid, gids, debug_flags, 561 rlimits, 0, 0, mount_external, se_info, se_name, false, fdsToClose); 562} 563 564static jint com_android_internal_os_Zygote_nativeForkSystemServer( 565 JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids, 566 jint debug_flags, jobjectArray rlimits, jlong permittedCapabilities, 567 jlong effectiveCapabilities) { 568 pid_t pid = ForkAndSpecializeCommon(env, uid, gid, gids, 569 debug_flags, rlimits, 570 permittedCapabilities, effectiveCapabilities, 571 MOUNT_EXTERNAL_NONE, NULL, NULL, true, NULL); 572 if (pid > 0) { 573 // The zygote process checks whether the child process has died or not. 574 ALOGI("System server process %d has been created", pid); 575 gSystemServerPid = pid; 576 // There is a slight window that the system server process has crashed 577 // but it went unnoticed because we haven't published its pid yet. So 578 // we recheck here just to make sure that all is well. 579 int status; 580 if (waitpid(pid, &status, WNOHANG) == pid) { 581 ALOGE("System server process %d has died. Restarting Zygote!", pid); 582 RuntimeAbort(env); 583 } 584 } 585 return pid; 586} 587 588static JNINativeMethod gMethods[] = { 589 { "nativeForkAndSpecialize", "(II[II[[IILjava/lang/String;Ljava/lang/String;[I)I", 590 (void *) com_android_internal_os_Zygote_nativeForkAndSpecialize }, 591 { "nativeForkSystemServer", "(II[II[[IJJ)I", 592 (void *) com_android_internal_os_Zygote_nativeForkSystemServer } 593}; 594 595int register_com_android_internal_os_Zygote(JNIEnv* env) { 596 gZygoteClass = (jclass) env->NewGlobalRef(env->FindClass(kZygoteClassName)); 597 if (gZygoteClass == NULL) { 598 RuntimeAbort(env); 599 } 600 gCallPostForkChildHooks = env->GetStaticMethodID(gZygoteClass, "callPostForkChildHooks", "(I)V"); 601 602 return AndroidRuntime::registerNativeMethods(env, "com/android/internal/os/Zygote", 603 gMethods, NELEM(gMethods)); 604} 605} // namespace android 606 607