content/zygote/zygote_main_linux.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/zygote/zygote_main.h"
   6
   7 #include <dlfcn.h>
   8 #include <fcntl.h>
   9 #include <pthread.h>
  10 #include <signal.h>
  11 #include <string.h>
  12 #include <sys/socket.h>
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #include <vector>
  17
  18 #include "base/basictypes.h"
  19 #include "base/bind.h"
  20 #include "base/command_line.h"
  21 #include "base/compiler_specific.h"
  22 #include "base/memory/scoped_vector.h"
  23 #include "base/native_library.h"
  24 #include "base/pickle.h"
  25 #include "base/posix/eintr_wrapper.h"
  26 #include "base/posix/unix_domain_socket_linux.h"
  27 #include "base/rand_util.h"
  28 #include "base/strings/safe_sprintf.h"
  29 #include "base/strings/string_number_conversions.h"
  30 #include "base/sys_info.h"
  31 #include "build/build_config.h"
  32 #include "content/common/child_process_sandbox_support_impl_linux.h"
  33 #include "content/common/font_config_ipc_linux.h"
  34 #include "content/common/sandbox_linux/sandbox_debug_handling_linux.h"
  35 #include "content/common/sandbox_linux/sandbox_linux.h"
  36 #include "content/common/zygote_commands_linux.h"
  37 #include "content/public/common/content_switches.h"
  38 #include "content/public/common/main_function_params.h"
  39 #include "content/public/common/sandbox_linux.h"
  40 #include "content/public/common/zygote_fork_delegate_linux.h"
  41 #include "content/zygote/zygote_linux.h"
  42 #include "crypto/nss_util.h"
  43 #include "sandbox/linux/services/credentials.h"
  44 #include "sandbox/linux/services/init_process_reaper.h"
  45 #include "sandbox/linux/services/libc_urandom_override.h"
  46 #include "sandbox/linux/services/namespace_sandbox.h"
  47 #include "sandbox/linux/services/thread_helpers.h"
  48 #include "sandbox/linux/suid/client/setuid_sandbox_client.h"
  49 #include "third_party/icu/source/i18n/unicode/timezone.h"
  50 #include "third_party/skia/include/ports/SkFontConfigInterface.h"
  51
  52 #if defined(OS_LINUX)
  53 #include <sys/prctl.h>
  54 #endif
  55
  56 #if defined(USE_OPENSSL)
  57 #include <openssl/rand.h>
  58 #endif
  59
  60 #if defined(ENABLE_PLUGINS)
  61 #include "content/common/pepper_plugin_list.h"
  62 #include "content/public/common/pepper_plugin_info.h"
  63 #endif
  64
  65 #if defined(ENABLE_WEBRTC)
  66 #include "third_party/libjingle/overrides/init_webrtc.h"
  67 #endif
  68
  69 #if defined(SANITIZER_COVERAGE)
  70 #include <sanitizer/common_interface_defs.h>
  71 #include <sanitizer/coverage_interface.h>
  72 #endif
  73
  74 namespace content {
  75
  76 namespace {
  77
  78 void CloseFds(const std::vector<int>& fds) {
  79   for (const auto& it : fds) {
  80     PCHECK(0 == IGNORE_EINTR(close(it)));
  81   }
  82 }
  83
  84 void RunTwoClosures(const base::Closure* first, const base::Closure* second) {
  85   first->Run();
  86   second->Run();
  87 }
  88
  89 }  // namespace
  90
  91 // See http://code.google.com/p/chromium/wiki/LinuxZygote
  92
  93 static void ProxyLocaltimeCallToBrowser(time_t input, struct tm* output,
  94                                         char* timezone_out,
  95                                         size_t timezone_out_len) {
  96   base::Pickle request;
  97   request.WriteInt(LinuxSandbox::METHOD_LOCALTIME);
  98   request.WriteString(
  99       std::string(reinterpret_cast<char*>(&input), sizeof(input)));
 100
 101   uint8_t reply_buf[512];
 102   const ssize_t r = base::UnixDomainSocket::SendRecvMsg(
 103       GetSandboxFD(), reply_buf, sizeof(reply_buf), NULL, request);
 104   if (r == -1) {
 105     memset(output, 0, sizeof(struct tm));
 106     return;
 107   }
 108
 109   base::Pickle reply(reinterpret_cast<char*>(reply_buf), r);
 110   base::PickleIterator iter(reply);
 111   std::string result, timezone;
 112   if (!iter.ReadString(&result) ||
 113       !iter.ReadString(&timezone) ||
 114       result.size() != sizeof(struct tm)) {
 115     memset(output, 0, sizeof(struct tm));
 116     return;
 117   }
 118
 119   memcpy(output, result.data(), sizeof(struct tm));
 120   if (timezone_out_len) {
 121     const size_t copy_len = std::min(timezone_out_len - 1, timezone.size());
 122     memcpy(timezone_out, timezone.data(), copy_len);
 123     timezone_out[copy_len] = 0;
 124     output->tm_zone = timezone_out;
 125   } else {
 126     output->tm_zone = NULL;
 127   }
 128 }
 129
 130 static bool g_am_zygote_or_renderer = false;
 131
 132 // Sandbox interception of libc calls.
 133 //
 134 // Because we are running in a sandbox certain libc calls will fail (localtime
 135 // being the motivating example - it needs to read /etc/localtime). We need to
 136 // intercept these calls and proxy them to the browser. However, these calls
 137 // may come from us or from our libraries. In some cases we can't just change
 138 // our code.
 139 //
 140 // It's for these cases that we have the following setup:
 141 //
 142 // We define global functions for those functions which we wish to override.
 143 // Since we will be first in the dynamic resolution order, the dynamic linker
 144 // will point callers to our versions of these functions. However, we have the
 145 // same binary for both the browser and the renderers, which means that our
 146 // overrides will apply in the browser too.
 147 //
 148 // The global |g_am_zygote_or_renderer| is true iff we are in a zygote or
 149 // renderer process. It's set in ZygoteMain and inherited by the renderers when
 150 // they fork. (This means that it'll be incorrect for global constructor
 151 // functions and before ZygoteMain is called - beware).
 152 //
 153 // Our replacement functions can check this global and either proxy
 154 // the call to the browser over the sandbox IPC
 155 // (http://code.google.com/p/chromium/wiki/LinuxSandboxIPC) or they can use
 156 // dlsym with RTLD_NEXT to resolve the symbol, ignoring any symbols in the
 157 // current module.
 158 //
 159 // Other avenues:
 160 //
 161 // Our first attempt involved some assembly to patch the GOT of the current
 162 // module. This worked, but was platform specific and doesn't catch the case
 163 // where a library makes a call rather than current module.
 164 //
 165 // We also considered patching the function in place, but this would again by
 166 // platform specific and the above technique seems to work well enough.
 167
 168 typedef struct tm* (*LocaltimeFunction)(const time_t* timep);
 169 typedef struct tm* (*LocaltimeRFunction)(const time_t* timep,
 170                                          struct tm* result);
 171
 172 static pthread_once_t g_libc_localtime_funcs_guard = PTHREAD_ONCE_INIT;
 173 static LocaltimeFunction g_libc_localtime;
 174 static LocaltimeFunction g_libc_localtime64;
 175 static LocaltimeRFunction g_libc_localtime_r;
 176 static LocaltimeRFunction g_libc_localtime64_r;
 177
 178 static void InitLibcLocaltimeFunctions() {
 179   g_libc_localtime = reinterpret_cast<LocaltimeFunction>(
 180       dlsym(RTLD_NEXT, "localtime"));
 181   g_libc_localtime64 = reinterpret_cast<LocaltimeFunction>(
 182       dlsym(RTLD_NEXT, "localtime64"));
 183   g_libc_localtime_r = reinterpret_cast<LocaltimeRFunction>(
 184       dlsym(RTLD_NEXT, "localtime_r"));
 185   g_libc_localtime64_r = reinterpret_cast<LocaltimeRFunction>(
 186       dlsym(RTLD_NEXT, "localtime64_r"));
 187
 188   if (!g_libc_localtime || !g_libc_localtime_r) {
 189     // http://code.google.com/p/chromium/issues/detail?id=16800
 190     //
 191     // Nvidia's libGL.so overrides dlsym for an unknown reason and replaces
 192     // it with a version which doesn't work. In this case we'll get a NULL
 193     // result. There's not a lot we can do at this point, so we just bodge it!
 194     LOG(ERROR) << "Your system is broken: dlsym doesn't work! This has been "
 195                   "reported to be caused by Nvidia's libGL. You should expect"
 196                   " time related functions to misbehave. "
 197                   "http://code.google.com/p/chromium/issues/detail?id=16800";
 198   }
 199
 200   if (!g_libc_localtime)
 201     g_libc_localtime = gmtime;
 202   if (!g_libc_localtime64)
 203     g_libc_localtime64 = g_libc_localtime;
 204   if (!g_libc_localtime_r)
 205     g_libc_localtime_r = gmtime_r;
 206   if (!g_libc_localtime64_r)
 207     g_libc_localtime64_r = g_libc_localtime_r;
 208 }
 209
 210 // Define localtime_override() function with asm name "localtime", so that all
 211 // references to localtime() will resolve to this function. Notice that we need
 212 // to set visibility attribute to "default" to export the symbol, as it is set
 213 // to "hidden" by default in chrome per build/common.gypi.
 214 __attribute__ ((__visibility__("default")))
 215 struct tm* localtime_override(const time_t* timep) __asm__ ("localtime");
 216
 217 __attribute__ ((__visibility__("default")))
 218 struct tm* localtime_override(const time_t* timep) {
 219   if (g_am_zygote_or_renderer) {
 220     static struct tm time_struct;
 221     static char timezone_string[64];
 222     ProxyLocaltimeCallToBrowser(*timep, &time_struct, timezone_string,
 223                                 sizeof(timezone_string));
 224     return &time_struct;
 225   } else {
 226     CHECK_EQ(0, pthread_once(&g_libc_localtime_funcs_guard,
 227                              InitLibcLocaltimeFunctions));
 228     struct tm* res = g_libc_localtime(timep);
 229 #if defined(MEMORY_SANITIZER)
 230     if (res) __msan_unpoison(res, sizeof(*res));
 231     if (res->tm_zone) __msan_unpoison_string(res->tm_zone);
 232 #endif
 233     return res;
 234   }
 235 }
 236
 237 // Use same trick to override localtime64(), localtime_r() and localtime64_r().
 238 __attribute__ ((__visibility__("default")))
 239 struct tm* localtime64_override(const time_t* timep) __asm__ ("localtime64");
 240
 241 __attribute__ ((__visibility__("default")))
 242 struct tm* localtime64_override(const time_t* timep) {
 243   if (g_am_zygote_or_renderer) {
 244     static struct tm time_struct;
 245     static char timezone_string[64];
 246     ProxyLocaltimeCallToBrowser(*timep, &time_struct, timezone_string,
 247                                 sizeof(timezone_string));
 248     return &time_struct;
 249   } else {
 250     CHECK_EQ(0, pthread_once(&g_libc_localtime_funcs_guard,
 251                              InitLibcLocaltimeFunctions));
 252     struct tm* res = g_libc_localtime64(timep);
 253 #if defined(MEMORY_SANITIZER)
 254     if (res) __msan_unpoison(res, sizeof(*res));
 255     if (res->tm_zone) __msan_unpoison_string(res->tm_zone);
 256 #endif
 257     return res;
 258   }
 259 }
 260
 261 __attribute__ ((__visibility__("default")))
 262 struct tm* localtime_r_override(const time_t* timep,
 263                                 struct tm* result) __asm__ ("localtime_r");
 264
 265 __attribute__ ((__visibility__("default")))
 266 struct tm* localtime_r_override(const time_t* timep, struct tm* result) {
 267   if (g_am_zygote_or_renderer) {
 268     ProxyLocaltimeCallToBrowser(*timep, result, NULL, 0);
 269     return result;
 270   } else {
 271     CHECK_EQ(0, pthread_once(&g_libc_localtime_funcs_guard,
 272                              InitLibcLocaltimeFunctions));
 273     struct tm* res = g_libc_localtime_r(timep, result);
 274 #if defined(MEMORY_SANITIZER)
 275     if (res) __msan_unpoison(res, sizeof(*res));
 276     if (res->tm_zone) __msan_unpoison_string(res->tm_zone);
 277 #endif
 278     return res;
 279   }
 280 }
 281
 282 __attribute__ ((__visibility__("default")))
 283 struct tm* localtime64_r_override(const time_t* timep,
 284                                   struct tm* result) __asm__ ("localtime64_r");
 285
 286 __attribute__ ((__visibility__("default")))
 287 struct tm* localtime64_r_override(const time_t* timep, struct tm* result) {
 288   if (g_am_zygote_or_renderer) {
 289     ProxyLocaltimeCallToBrowser(*timep, result, NULL, 0);
 290     return result;
 291   } else {
 292     CHECK_EQ(0, pthread_once(&g_libc_localtime_funcs_guard,
 293                              InitLibcLocaltimeFunctions));
 294     struct tm* res = g_libc_localtime64_r(timep, result);
 295 #if defined(MEMORY_SANITIZER)
 296     if (res) __msan_unpoison(res, sizeof(*res));
 297     if (res->tm_zone) __msan_unpoison_string(res->tm_zone);
 298 #endif
 299     return res;
 300   }
 301 }
 302
 303 #if defined(ENABLE_PLUGINS)
 304 // Loads the (native) libraries but does not initialize them (i.e., does not
 305 // call PPP_InitializeModule). This is needed by the zygote on Linux to get
 306 // access to the plugins before entering the sandbox.
 307 void PreloadPepperPlugins() {
 308   std::vector<PepperPluginInfo> plugins;
 309   ComputePepperPluginList(&plugins);
 310   for (size_t i = 0; i < plugins.size(); ++i) {
 311     if (!plugins[i].is_internal) {
 312       base::NativeLibraryLoadError error;
 313       base::NativeLibrary library = base::LoadNativeLibrary(plugins[i].path,
 314                                                             &error);
 315       VLOG_IF(1, !library) << "Unable to load plugin "
 316                            << plugins[i].path.value() << " "
 317                            << error.ToString();
 318
 319       (void)library;  // Prevent release-mode warning.
 320     }
 321   }
 322 }
 323 #endif
 324
 325 // This function triggers the static and lazy construction of objects that need
 326 // to be created before imposing the sandbox.
 327 static void ZygotePreSandboxInit() {
 328   base::RandUint64();
 329
 330   base::SysInfo::AmountOfPhysicalMemory();
 331   base::SysInfo::MaxSharedMemorySize();
 332   base::SysInfo::NumberOfProcessors();
 333
 334   // ICU DateFormat class (used in base/time_format.cc) needs to get the
 335   // Olson timezone ID by accessing the zoneinfo files on disk. After
 336   // TimeZone::createDefault is called once here, the timezone ID is
 337   // cached and there's no more need to access the file system.
 338   scoped_ptr<icu::TimeZone> zone(icu::TimeZone::createDefault());
 339
 340 #if defined(USE_NSS_CERTS)
 341   // NSS libraries are loaded before sandbox is activated. This is to allow
 342   // successful initialization of NSS which tries to load extra library files.
 343   crypto::LoadNSSLibraries();
 344 #elif defined(USE_OPENSSL)
 345   // Read a random byte in order to cause BoringSSL to open a file descriptor
 346   // for /dev/urandom.
 347   uint8_t scratch;
 348   RAND_bytes(&scratch, 1);
 349 #else
 350   // It's possible that another hypothetical crypto stack would not require
 351   // pre-sandbox init, but more likely this is just a build configuration error.
 352   #error Which SSL library are you using?
 353 #endif
 354 #if defined(ENABLE_PLUGINS)
 355   // Ensure access to the Pepper plugins before the sandbox is turned on.
 356   PreloadPepperPlugins();
 357 #endif
 358 #if defined(ENABLE_WEBRTC)
 359   InitializeWebRtcModule();
 360 #endif
 361   SkFontConfigInterface::SetGlobal(
 362       new FontConfigIPC(GetSandboxFD()))->unref();
 363 }
 364
 365 static bool CreateInitProcessReaper(base::Closure* post_fork_parent_callback) {
 366   // The current process becomes init(1), this function returns from a
 367   // newly created process.
 368   const bool init_created =
 369       sandbox::CreateInitProcessReaper(post_fork_parent_callback);
 370   if (!init_created) {
 371     LOG(ERROR) << "Error creating an init process to reap zombies";
 372     return false;
 373   }
 374   return true;
 375 }
 376
 377 // Enter the setuid sandbox. This requires the current process to have been
 378 // created through the setuid sandbox.
 379 static bool EnterSuidSandbox(sandbox::SetuidSandboxClient* setuid_sandbox,
 380                              base::Closure* post_fork_parent_callback) {
 381   DCHECK(setuid_sandbox);
 382   DCHECK(setuid_sandbox->IsSuidSandboxChild());
 383
 384   // Use the SUID sandbox.  This still allows the seccomp sandbox to
 385   // be enabled by the process later.
 386
 387   if (!setuid_sandbox->IsSuidSandboxUpToDate()) {
 388     LOG(WARNING) <<
 389         "You are using a wrong version of the setuid binary!\n"
 390         "Please read "
 391         "https://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment."
 392         "\n\n";
 393   }
 394
 395   if (!setuid_sandbox->ChrootMe())
 396     return false;
 397
 398   if (setuid_sandbox->IsInNewPIDNamespace()) {
 399     CHECK_EQ(1, getpid())
 400         << "The SUID sandbox created a new PID namespace but Zygote "
 401            "is not the init process. Please, make sure the SUID "
 402            "binary is up to date.";
 403   }
 404
 405   if (getpid() == 1) {
 406     // The setuid sandbox has created a new PID namespace and we need
 407     // to assume the role of init.
 408     CHECK(CreateInitProcessReaper(post_fork_parent_callback));
 409   }
 410
 411   CHECK(SandboxDebugHandling::SetDumpableStatusAndHandlers());
 412   return true;
 413 }
 414
 415 static void DropAllCapabilities(int proc_fd) {
 416   CHECK(sandbox::Credentials::DropAllCapabilities(proc_fd));
 417 }
 418
 419 static void EnterNamespaceSandbox(LinuxSandbox* linux_sandbox,
 420                                   base::Closure* post_fork_parent_callback) {
 421   linux_sandbox->EngageNamespaceSandbox();
 422
 423   if (getpid() == 1) {
 424     base::Closure drop_all_caps_callback =
 425         base::Bind(&DropAllCapabilities, linux_sandbox->proc_fd());
 426     base::Closure callback = base::Bind(
 427         &RunTwoClosures, &drop_all_caps_callback, post_fork_parent_callback);
 428     CHECK(CreateInitProcessReaper(&callback));
 429   }
 430 }
 431
 432 #if defined(SANITIZER_COVERAGE)
 433 const size_t kSanitizerMaxMessageLength = 1 * 1024 * 1024;
 434
 435 // A helper process which collects code coverage data from the renderers over a
 436 // socket and dumps it to a file. See http://crbug.com/336212 for discussion.
 437 static void SanitizerCoverageHelper(int socket_fd, int file_fd) {
 438   scoped_ptr<char[]> buffer(new char[kSanitizerMaxMessageLength]);
 439   while (true) {
 440     ssize_t received_size = HANDLE_EINTR(
 441         recv(socket_fd, buffer.get(), kSanitizerMaxMessageLength, 0));
 442     PCHECK(received_size >= 0);
 443     if (received_size == 0)
 444       // All clients have closed the socket. We should die.
 445       _exit(0);
 446     PCHECK(file_fd >= 0);
 447     ssize_t written_size = 0;
 448     while (written_size < received_size) {
 449       ssize_t write_res =
 450           HANDLE_EINTR(write(file_fd, buffer.get() + written_size,
 451                              received_size - written_size));
 452       PCHECK(write_res >= 0);
 453       written_size += write_res;
 454     }
 455     PCHECK(0 == HANDLE_EINTR(fsync(file_fd)));
 456   }
 457 }
 458
 459 // fds[0] is the read end, fds[1] is the write end.
 460 static void CreateSanitizerCoverageSocketPair(int fds[2]) {
 461   PCHECK(0 == socketpair(AF_UNIX, SOCK_SEQPACKET, 0, fds));
 462   PCHECK(0 == shutdown(fds[0], SHUT_WR));
 463   PCHECK(0 == shutdown(fds[1], SHUT_RD));
 464 }
 465
 466 static pid_t ForkSanitizerCoverageHelper(
 467     int child_fd,
 468     int parent_fd,
 469     base::ScopedFD file_fd,
 470     const std::vector<int>& extra_fds_to_close) {
 471   pid_t pid = fork();
 472   PCHECK(pid >= 0);
 473   if (pid == 0) {
 474     // In the child.
 475     PCHECK(0 == IGNORE_EINTR(close(parent_fd)));
 476     CloseFds(extra_fds_to_close);
 477     SanitizerCoverageHelper(child_fd, file_fd.get());
 478     _exit(0);
 479   } else {
 480     // In the parent.
 481     PCHECK(0 == IGNORE_EINTR(close(child_fd)));
 482     return pid;
 483   }
 484 }
 485
 486 #endif  // defined(SANITIZER_COVERAGE)
 487
 488 static void EnterLayerOneSandbox(LinuxSandbox* linux_sandbox,
 489                                  const bool using_layer1_sandbox,
 490                                  base::Closure* post_fork_parent_callback) {
 491   DCHECK(linux_sandbox);
 492
 493   ZygotePreSandboxInit();
 494
 495   // Check that the pre-sandbox initialization didn't spawn threads.
 496 #if !defined(THREAD_SANITIZER)
 497   DCHECK(sandbox::ThreadHelpers::IsSingleThreaded());
 498 #endif
 499
 500   sandbox::SetuidSandboxClient* setuid_sandbox =
 501       linux_sandbox->setuid_sandbox_client();
 502   if (setuid_sandbox->IsSuidSandboxChild()) {
 503     CHECK(EnterSuidSandbox(setuid_sandbox, post_fork_parent_callback))
 504         << "Failed to enter setuid sandbox";
 505   } else if (sandbox::NamespaceSandbox::InNewUserNamespace()) {
 506     EnterNamespaceSandbox(linux_sandbox, post_fork_parent_callback);
 507   } else {
 508     CHECK(!using_layer1_sandbox);
 509   }
 510 }
 511
 512 bool ZygoteMain(const MainFunctionParams& params,
 513                 ScopedVector<ZygoteForkDelegate> fork_delegates) {
 514   g_am_zygote_or_renderer = true;
 515   sandbox::InitLibcUrandomOverrides();
 516
 517   std::vector<int> fds_to_close_post_fork;
 518
 519   LinuxSandbox* linux_sandbox = LinuxSandbox::GetInstance();
 520
 521 #if defined(SANITIZER_COVERAGE)
 522   const std::string sancov_file_name =
 523       "zygote." + base::Uint64ToString(base::RandUint64());
 524   base::ScopedFD sancov_file_fd(
 525       __sanitizer_maybe_open_cov_file(sancov_file_name.c_str()));
 526   int sancov_socket_fds[2] = {-1, -1};
 527   CreateSanitizerCoverageSocketPair(sancov_socket_fds);
 528   linux_sandbox->sanitizer_args()->coverage_sandboxed = 1;
 529   linux_sandbox->sanitizer_args()->coverage_fd = sancov_socket_fds[1];
 530   linux_sandbox->sanitizer_args()->coverage_max_block_size =
 531       kSanitizerMaxMessageLength;
 532   // Zygote termination will block until the helper process exits, which will
 533   // not happen until the write end of the socket is closed everywhere. Make
 534   // sure the init process does not hold on to it.
 535   fds_to_close_post_fork.push_back(sancov_socket_fds[0]);
 536   fds_to_close_post_fork.push_back(sancov_socket_fds[1]);
 537 #endif  // SANITIZER_COVERAGE
 538
 539   // Skip pre-initializing sandbox under --no-sandbox for crbug.com/444900.
 540   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
 541           switches::kNoSandbox)) {
 542     // This will pre-initialize the various sandboxes that need it.
 543     linux_sandbox->PreinitializeSandbox();
 544   }
 545
 546   const bool using_setuid_sandbox =
 547       linux_sandbox->setuid_sandbox_client()->IsSuidSandboxChild();
 548   const bool using_namespace_sandbox =
 549       sandbox::NamespaceSandbox::InNewUserNamespace();
 550   const bool using_layer1_sandbox =
 551       using_setuid_sandbox || using_namespace_sandbox;
 552
 553   if (using_setuid_sandbox) {
 554     linux_sandbox->setuid_sandbox_client()->CloseDummyFile();
 555   }
 556
 557   if (using_layer1_sandbox) {
 558     // Let the ZygoteHost know we're booting up.
 559     CHECK(base::UnixDomainSocket::SendMsg(kZygoteSocketPairFd,
 560                                           kZygoteBootMessage,
 561                                           sizeof(kZygoteBootMessage),
 562                                           std::vector<int>()));
 563   }
 564
 565   VLOG(1) << "ZygoteMain: initializing " << fork_delegates.size()
 566           << " fork delegates";
 567   for (ZygoteForkDelegate* fork_delegate : fork_delegates) {
 568     fork_delegate->Init(GetSandboxFD(), using_layer1_sandbox);
 569   }
 570
 571   const std::vector<int> sandbox_fds_to_close_post_fork =
 572       linux_sandbox->GetFileDescriptorsToClose();
 573
 574   fds_to_close_post_fork.insert(fds_to_close_post_fork.end(),
 575                                 sandbox_fds_to_close_post_fork.begin(),
 576                                 sandbox_fds_to_close_post_fork.end());
 577   base::Closure post_fork_parent_callback =
 578       base::Bind(&CloseFds, fds_to_close_post_fork);
 579
 580   // Turn on the first layer of the sandbox if the configuration warrants it.
 581   EnterLayerOneSandbox(linux_sandbox, using_layer1_sandbox,
 582                        &post_fork_parent_callback);
 583
 584   // Extra children and file descriptors created that the Zygote must have
 585   // knowledge of.
 586   std::vector<pid_t> extra_children;
 587   std::vector<int> extra_fds;
 588
 589 #if defined(SANITIZER_COVERAGE)
 590   pid_t sancov_helper_pid = ForkSanitizerCoverageHelper(
 591       sancov_socket_fds[0], sancov_socket_fds[1], sancov_file_fd.Pass(),
 592       sandbox_fds_to_close_post_fork);
 593   // It's important that the zygote reaps the helper before dying. Otherwise,
 594   // the destruction of the PID namespace could kill the helper before it
 595   // completes its I/O tasks. |sancov_helper_pid| will exit once the last
 596   // renderer holding the write end of |sancov_socket_fds| closes it.
 597   extra_children.push_back(sancov_helper_pid);
 598   // Sanitizer code in the renderers will inherit the write end of the socket
 599   // from the zygote. We must keep it open until the very end of the zygote's
 600   // lifetime, even though we don't explicitly use it.
 601   extra_fds.push_back(sancov_socket_fds[1]);
 602 #endif  // SANITIZER_COVERAGE
 603
 604   const int sandbox_flags = linux_sandbox->GetStatus();
 605
 606   const bool setuid_sandbox_engaged = sandbox_flags & kSandboxLinuxSUID;
 607   CHECK_EQ(using_setuid_sandbox, setuid_sandbox_engaged);
 608
 609   const bool namespace_sandbox_engaged = sandbox_flags & kSandboxLinuxUserNS;
 610   CHECK_EQ(using_namespace_sandbox, namespace_sandbox_engaged);
 611
 612   Zygote zygote(sandbox_flags, fork_delegates.Pass(), extra_children,
 613                 extra_fds);
 614   // This function call can return multiple times, once per fork().
 615   return zygote.ProcessRequests();
 616 }
 617
 618 }  // namespace content