content/zygote/zygote_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_linux.h"
   6
   7 #include <fcntl.h>
   8 #include <string.h>
   9 #include <sys/socket.h>
  10 #include <sys/types.h>
  11 #include <sys/wait.h>
  12
  13 #include "base/command_line.h"
  14 #include "base/debug/trace_event.h"
  15 #include "base/file_util.h"
  16 #include "base/linux_util.h"
  17 #include "base/logging.h"
  18 #include "base/pickle.h"
  19 #include "base/posix/eintr_wrapper.h"
  20 #include "base/posix/global_descriptors.h"
  21 #include "base/posix/unix_domain_socket_linux.h"
  22 #include "base/process/kill.h"
  23 #include "content/common/child_process_sandbox_support_impl_linux.h"
  24 #include "content/common/sandbox_linux.h"
  25 #include "content/common/set_process_title.h"
  26 #include "content/common/zygote_commands_linux.h"
  27 #include "content/public/common/content_descriptors.h"
  28 #include "content/public/common/result_codes.h"
  29 #include "content/public/common/sandbox_linux.h"
  30 #include "content/public/common/zygote_fork_delegate_linux.h"
  31 #include "ipc/ipc_channel.h"
  32 #include "ipc/ipc_switches.h"
  33
  34 // See http://code.google.com/p/chromium/wiki/LinuxZygote
  35
  36 namespace content {
  37
  38 namespace {
  39
  40 // NOP function. See below where this handler is installed.
  41 void SIGCHLDHandler(int signal) {
  42 }
  43
  44 int LookUpFd(const base::GlobalDescriptors::Mapping& fd_mapping, uint32_t key) {
  45   for (size_t index = 0; index < fd_mapping.size(); ++index) {
  46     if (fd_mapping[index].first == key)
  47       return fd_mapping[index].second;
  48   }
  49   return -1;
  50 }
  51
  52 }  // namespace
  53
  54 Zygote::Zygote(int sandbox_flags,
  55                ZygoteForkDelegate* helper)
  56     : sandbox_flags_(sandbox_flags),
  57       helper_(helper),
  58       initial_uma_sample_(0),
  59       initial_uma_boundary_value_(0) {
  60   if (helper_) {
  61     helper_->InitialUMA(&initial_uma_name_,
  62                         &initial_uma_sample_,
  63                         &initial_uma_boundary_value_);
  64   }
  65 }
  66
  67 Zygote::~Zygote() {
  68 }
  69
  70 bool Zygote::ProcessRequests() {
  71   // A SOCK_SEQPACKET socket is installed in fd 3. We get commands from the
  72   // browser on it.
  73   // A SOCK_DGRAM is installed in fd 5. This is the sandbox IPC channel.
  74   // See http://code.google.com/p/chromium/wiki/LinuxSandboxIPC
  75
  76   // We need to accept SIGCHLD, even though our handler is a no-op because
  77   // otherwise we cannot wait on children. (According to POSIX 2001.)
  78   struct sigaction action;
  79   memset(&action, 0, sizeof(action));
  80   action.sa_handler = &SIGCHLDHandler;
  81   CHECK(sigaction(SIGCHLD, &action, NULL) == 0);
  82
  83   if (UsingSUIDSandbox()) {
  84     // Let the ZygoteHost know we are ready to go.
  85     // The receiving code is in content/browser/zygote_host_linux.cc.
  86     std::vector<int> empty;
  87     bool r = UnixDomainSocket::SendMsg(kZygoteSocketPairFd,
  88                                        kZygoteHelloMessage,
  89                                        sizeof(kZygoteHelloMessage), empty);
  90 #if defined(OS_CHROMEOS)
  91     LOG_IF(WARNING, !r) << "Sending zygote magic failed";
  92     // Exit normally on chromeos because session manager may send SIGTERM
  93     // right after the process starts and it may fail to send zygote magic
  94     // number to browser process.
  95     if (!r)
  96       _exit(RESULT_CODE_NORMAL_EXIT);
  97 #else
  98     CHECK(r) << "Sending zygote magic failed";
  99 #endif
 100   }
 101
 102   for (;;) {
 103     // This function call can return multiple times, once per fork().
 104     if (HandleRequestFromBrowser(kZygoteSocketPairFd))
 105       return true;
 106   }
 107 }
 108
 109 bool Zygote::GetProcessInfo(base::ProcessHandle pid,
 110                             ZygoteProcessInfo* process_info) {
 111   DCHECK(process_info);
 112   const ZygoteProcessMap::const_iterator it = process_info_map_.find(pid);
 113   if (it == process_info_map_.end()) {
 114     return false;
 115   }
 116   *process_info = it->second;
 117   return true;
 118 }
 119
 120 bool Zygote::UsingSUIDSandbox() const {
 121   return sandbox_flags_ & kSandboxLinuxSUID;
 122 }
 123
 124 bool Zygote::HandleRequestFromBrowser(int fd) {
 125   std::vector<int> fds;
 126   char buf[kZygoteMaxMessageLength];
 127   const ssize_t len = UnixDomainSocket::RecvMsg(fd, buf, sizeof(buf), &fds);
 128
 129   if (len == 0 || (len == -1 && errno == ECONNRESET)) {
 130     // EOF from the browser. We should die.
 131     _exit(0);
 132     return false;
 133   }
 134
 135   if (len == -1) {
 136     PLOG(ERROR) << "Error reading message from browser";
 137     return false;
 138   }
 139
 140   Pickle pickle(buf, len);
 141   PickleIterator iter(pickle);
 142
 143   int kind;
 144   if (pickle.ReadInt(&iter, &kind)) {
 145     switch (kind) {
 146       case kZygoteCommandFork:
 147         // This function call can return multiple times, once per fork().
 148         return HandleForkRequest(fd, pickle, iter, fds);
 149
 150       case kZygoteCommandReap:
 151         if (!fds.empty())
 152           break;
 153         HandleReapRequest(fd, pickle, iter);
 154         return false;
 155       case kZygoteCommandGetTerminationStatus:
 156         if (!fds.empty())
 157           break;
 158         HandleGetTerminationStatus(fd, pickle, iter);
 159         return false;
 160       case kZygoteCommandGetSandboxStatus:
 161         HandleGetSandboxStatus(fd, pickle, iter);
 162         return false;
 163       default:
 164         NOTREACHED();
 165         break;
 166     }
 167   }
 168
 169   LOG(WARNING) << "Error parsing message from browser";
 170   for (std::vector<int>::const_iterator
 171        i = fds.begin(); i != fds.end(); ++i)
 172     close(*i);
 173   return false;
 174 }
 175
 176 // TODO(jln): remove callers to this broken API. See crbug.com/274855.
 177 void Zygote::HandleReapRequest(int fd,
 178                                const Pickle& pickle,
 179                                PickleIterator iter) {
 180   base::ProcessId child;
 181
 182   if (!pickle.ReadInt(&iter, &child)) {
 183     LOG(WARNING) << "Error parsing reap request from browser";
 184     return;
 185   }
 186
 187   ZygoteProcessInfo child_info;
 188   if (!GetProcessInfo(child, &child_info)) {
 189     LOG(ERROR) << "Child not found!";
 190     NOTREACHED();
 191     return;
 192   }
 193
 194   if (!child_info.started_from_helper) {
 195     // TODO(jln): this old code is completely broken. See crbug.com/274855.
 196     base::EnsureProcessTerminated(child_info.internal_pid);
 197   } else {
 198     // For processes from the helper, send a GetTerminationStatus request
 199     // with known_dead set to true.
 200     // This is not perfect, as the process may be killed instantly, but is
 201     // better than ignoring the request.
 202     base::TerminationStatus status;
 203     int exit_code;
 204     bool got_termination_status =
 205         GetTerminationStatus(child, true /* known_dead */, &status, &exit_code);
 206     DCHECK(got_termination_status);
 207   }
 208   process_info_map_.erase(child);
 209 }
 210
 211 bool Zygote::GetTerminationStatus(base::ProcessHandle real_pid,
 212                                   bool known_dead,
 213                                   base::TerminationStatus* status,
 214                                   int* exit_code) {
 215
 216   ZygoteProcessInfo child_info;
 217   if (!GetProcessInfo(real_pid, &child_info)) {
 218     LOG(ERROR) << "Zygote::GetTerminationStatus for unknown PID "
 219                << real_pid;
 220     NOTREACHED();
 221     return false;
 222   }
 223   // We know about |real_pid|.
 224   const base::ProcessHandle child = child_info.internal_pid;
 225   if (child_info.started_from_helper) {
 226     // Let the helper handle the request.
 227     DCHECK(helper_);
 228     if (!helper_->GetTerminationStatus(child, known_dead, status, exit_code)) {
 229       return false;
 230     }
 231   } else {
 232     // Handle the request directly.
 233     if (known_dead) {
 234       *status = base::GetKnownDeadTerminationStatus(child, exit_code);
 235     } else {
 236       // We don't know if the process is dying, so get its status but don't
 237       // wait.
 238       *status = base::GetTerminationStatus(child, exit_code);
 239     }
 240   }
 241   // Successfully got a status for |real_pid|.
 242   if (*status != base::TERMINATION_STATUS_STILL_RUNNING) {
 243     // Time to forget about this process.
 244     process_info_map_.erase(real_pid);
 245   }
 246   return true;
 247 }
 248
 249 void Zygote::HandleGetTerminationStatus(int fd,
 250                                         const Pickle& pickle,
 251                                         PickleIterator iter) {
 252   bool known_dead;
 253   base::ProcessHandle child_requested;
 254
 255   if (!pickle.ReadBool(&iter, &known_dead) ||
 256       !pickle.ReadInt(&iter, &child_requested)) {
 257     LOG(WARNING) << "Error parsing GetTerminationStatus request "
 258                  << "from browser";
 259     return;
 260   }
 261
 262   base::TerminationStatus status;
 263   int exit_code;
 264
 265   bool got_termination_status =
 266       GetTerminationStatus(child_requested, known_dead, &status, &exit_code);
 267   if (!got_termination_status) {
 268     // Assume that if we can't find the child in the sandbox, then
 269     // it terminated normally.
 270     NOTREACHED();
 271     status = base::TERMINATION_STATUS_NORMAL_TERMINATION;
 272     exit_code = RESULT_CODE_NORMAL_EXIT;
 273   }
 274
 275   Pickle write_pickle;
 276   write_pickle.WriteInt(static_cast<int>(status));
 277   write_pickle.WriteInt(exit_code);
 278   ssize_t written =
 279       HANDLE_EINTR(write(fd, write_pickle.data(), write_pickle.size()));
 280   if (written != static_cast<ssize_t>(write_pickle.size()))
 281     PLOG(ERROR) << "write";
 282 }
 283
 284 int Zygote::ForkWithRealPid(const std::string& process_type,
 285                             const base::GlobalDescriptors::Mapping& fd_mapping,
 286                             const std::string& channel_switch,
 287                             std::string* uma_name,
 288                             int* uma_sample,
 289                             int* uma_boundary_value) {
 290   const bool use_helper = (helper_ && helper_->CanHelp(process_type,
 291                                                        uma_name,
 292                                                        uma_sample,
 293                                                        uma_boundary_value));
 294   int dummy_fd;
 295   ino_t dummy_inode;
 296   int pipe_fds[2] = { -1, -1 };
 297   base::ProcessId pid = 0;
 298
 299   dummy_fd = socket(PF_UNIX, SOCK_DGRAM, 0);
 300   if (dummy_fd < 0) {
 301     LOG(ERROR) << "Failed to create dummy FD";
 302     goto error;
 303   }
 304   if (!base::FileDescriptorGetInode(&dummy_inode, dummy_fd)) {
 305     LOG(ERROR) << "Failed to get inode for dummy FD";
 306     goto error;
 307   }
 308   if (pipe(pipe_fds) != 0) {
 309     LOG(ERROR) << "Failed to create pipe";
 310     goto error;
 311   }
 312
 313   if (use_helper) {
 314     std::vector<int> fds;
 315     int ipc_channel_fd = LookUpFd(fd_mapping, kPrimaryIPCChannel);
 316     if (ipc_channel_fd < 0) {
 317       DLOG(ERROR) << "Failed to find kPrimaryIPCChannel in FD mapping";
 318       goto error;
 319     }
 320     fds.push_back(ipc_channel_fd);  // kBrowserFDIndex
 321     fds.push_back(dummy_fd);  // kDummyFDIndex
 322     fds.push_back(pipe_fds[0]);  // kParentFDIndex
 323     pid = helper_->Fork(fds);
 324   } else {
 325     pid = fork();
 326   }
 327   if (pid < 0) {
 328     goto error;
 329   } else if (pid == 0) {
 330     // In the child process.
 331     close(pipe_fds[1]);
 332     base::ProcessId real_pid;
 333     // Wait until the parent process has discovered our PID.  We
 334     // should not fork any child processes (which the seccomp
 335     // sandbox does) until then, because that can interfere with the
 336     // parent's discovery of our PID.
 337     if (!base::ReadFromFD(pipe_fds[0], reinterpret_cast<char*>(&real_pid),
 338                           sizeof(real_pid))) {
 339       LOG(FATAL) << "Failed to synchronise with parent zygote process";
 340     }
 341     if (real_pid <= 0) {
 342       LOG(FATAL) << "Invalid pid from parent zygote";
 343     }
 344 #if defined(OS_LINUX)
 345     // Sandboxed processes need to send the global, non-namespaced PID when
 346     // setting up an IPC channel to their parent.
 347     IPC::Channel::SetGlobalPid(real_pid);
 348     // Force the real PID so chrome event data have a PID that corresponds
 349     // to system trace event data.
 350     base::debug::TraceLog::GetInstance()->SetProcessID(
 351         static_cast<int>(real_pid));
 352 #endif
 353     close(pipe_fds[0]);
 354     close(dummy_fd);
 355     return 0;
 356   } else {
 357     // In the parent process.
 358     close(dummy_fd);
 359     dummy_fd = -1;
 360     close(pipe_fds[0]);
 361     pipe_fds[0] = -1;
 362     base::ProcessId real_pid;
 363     if (UsingSUIDSandbox()) {
 364       uint8_t reply_buf[512];
 365       Pickle request;
 366       request.WriteInt(LinuxSandbox::METHOD_GET_CHILD_WITH_INODE);
 367       request.WriteUInt64(dummy_inode);
 368
 369       const ssize_t r = UnixDomainSocket::SendRecvMsg(
 370           GetSandboxFD(), reply_buf, sizeof(reply_buf), NULL,
 371           request);
 372       if (r == -1) {
 373         LOG(ERROR) << "Failed to get child process's real PID";
 374         goto error;
 375       }
 376
 377       Pickle reply(reinterpret_cast<char*>(reply_buf), r);
 378       PickleIterator iter(reply);
 379       if (!reply.ReadInt(&iter, &real_pid))
 380         goto error;
 381       if (real_pid <= 0) {
 382         // METHOD_GET_CHILD_WITH_INODE failed. Did the child die already?
 383         LOG(ERROR) << "METHOD_GET_CHILD_WITH_INODE failed";
 384         goto error;
 385       }
 386     } else {
 387       // If no SUID sandbox is involved then no pid translation is
 388       // necessary.
 389       real_pid = pid;
 390     }
 391
 392     // Now set-up this process to be tracked by the Zygote.
 393     if (process_info_map_.find(real_pid) != process_info_map_.end()) {
 394       LOG(ERROR) << "Already tracking PID " << real_pid;
 395       NOTREACHED();
 396     }
 397     process_info_map_[real_pid].internal_pid = pid;
 398     process_info_map_[real_pid].started_from_helper = use_helper;
 399
 400     if (use_helper) {
 401       if (!helper_->AckChild(pipe_fds[1], channel_switch)) {
 402         LOG(ERROR) << "Failed to synchronise with zygote fork helper";
 403         goto error;
 404       }
 405     } else {
 406       int written =
 407           HANDLE_EINTR(write(pipe_fds[1], &real_pid, sizeof(real_pid)));
 408       if (written != sizeof(real_pid)) {
 409         LOG(ERROR) << "Failed to synchronise with child process";
 410         goto error;
 411       }
 412     }
 413     close(pipe_fds[1]);
 414     return real_pid;
 415   }
 416
 417  error:
 418   if (pid > 0) {
 419     if (waitpid(pid, NULL, WNOHANG) == -1)
 420       LOG(ERROR) << "Failed to wait for process";
 421   }
 422   if (dummy_fd >= 0)
 423     close(dummy_fd);
 424   if (pipe_fds[0] >= 0)
 425     close(pipe_fds[0]);
 426   if (pipe_fds[1] >= 0)
 427     close(pipe_fds[1]);
 428   return -1;
 429 }
 430
 431 base::ProcessId Zygote::ReadArgsAndFork(const Pickle& pickle,
 432                                         PickleIterator iter,
 433                                         std::vector<int>& fds,
 434                                         std::string* uma_name,
 435                                         int* uma_sample,
 436                                         int* uma_boundary_value) {
 437   std::vector<std::string> args;
 438   int argc = 0;
 439   int numfds = 0;
 440   base::GlobalDescriptors::Mapping mapping;
 441   std::string process_type;
 442   std::string channel_id;
 443   const std::string channel_id_prefix = std::string("--")
 444       + switches::kProcessChannelID + std::string("=");
 445
 446   if (!pickle.ReadString(&iter, &process_type))
 447     return -1;
 448   if (!pickle.ReadInt(&iter, &argc))
 449     return -1;
 450
 451   for (int i = 0; i < argc; ++i) {
 452     std::string arg;
 453     if (!pickle.ReadString(&iter, &arg))
 454       return -1;
 455     args.push_back(arg);
 456     if (arg.compare(0, channel_id_prefix.length(), channel_id_prefix) == 0)
 457       channel_id = arg;
 458   }
 459
 460   if (!pickle.ReadInt(&iter, &numfds))
 461     return -1;
 462   if (numfds != static_cast<int>(fds.size()))
 463     return -1;
 464
 465   for (int i = 0; i < numfds; ++i) {
 466     base::GlobalDescriptors::Key key;
 467     if (!pickle.ReadUInt32(&iter, &key))
 468       return -1;
 469     mapping.push_back(std::make_pair(key, fds[i]));
 470   }
 471
 472   mapping.push_back(std::make_pair(
 473       static_cast<uint32_t>(kSandboxIPCChannel), GetSandboxFD()));
 474
 475   // Returns twice, once per process.
 476   base::ProcessId child_pid = ForkWithRealPid(process_type, mapping, channel_id,
 477                                               uma_name, uma_sample,
 478                                               uma_boundary_value);
 479   if (!child_pid) {
 480     // This is the child process.
 481
 482     close(kZygoteSocketPairFd);  // Our socket from the browser.
 483     if (UsingSUIDSandbox())
 484       close(kZygoteIdFd);  // Another socket from the browser.
 485     base::GlobalDescriptors::GetInstance()->Reset(mapping);
 486
 487     // Reset the process-wide command line to our new command line.
 488     CommandLine::Reset();
 489     CommandLine::Init(0, NULL);
 490     CommandLine::ForCurrentProcess()->InitFromArgv(args);
 491
 492     // Update the process title. The argv was already cached by the call to
 493     // SetProcessTitleFromCommandLine in ChromeMain, so we can pass NULL here
 494     // (we don't have the original argv at this point).
 495     SetProcessTitleFromCommandLine(NULL);
 496   } else if (child_pid < 0) {
 497     LOG(ERROR) << "Zygote could not fork: process_type " << process_type
 498         << " numfds " << numfds << " child_pid " << child_pid;
 499   }
 500   return child_pid;
 501 }
 502
 503 bool Zygote::HandleForkRequest(int fd,
 504                                const Pickle& pickle,
 505                                PickleIterator iter,
 506                                std::vector<int>& fds) {
 507   std::string uma_name;
 508   int uma_sample;
 509   int uma_boundary_value;
 510   base::ProcessId child_pid = ReadArgsAndFork(pickle, iter, fds,
 511                                               &uma_name, &uma_sample,
 512                                               &uma_boundary_value);
 513   if (child_pid == 0)
 514     return true;
 515   for (std::vector<int>::const_iterator
 516        i = fds.begin(); i != fds.end(); ++i)
 517     close(*i);
 518   if (uma_name.empty()) {
 519     // There is no UMA report from this particular fork.
 520     // Use the initial UMA report if any, and clear that record for next time.
 521     // Note the swap method here is the efficient way to do this, since
 522     // we know uma_name is empty.
 523     uma_name.swap(initial_uma_name_);
 524     uma_sample = initial_uma_sample_;
 525     uma_boundary_value = initial_uma_boundary_value_;
 526   }
 527   // Must always send reply, as ZygoteHost blocks while waiting for it.
 528   Pickle reply_pickle;
 529   reply_pickle.WriteInt(child_pid);
 530   reply_pickle.WriteString(uma_name);
 531   if (!uma_name.empty()) {
 532     reply_pickle.WriteInt(uma_sample);
 533     reply_pickle.WriteInt(uma_boundary_value);
 534   }
 535   if (HANDLE_EINTR(write(fd, reply_pickle.data(), reply_pickle.size())) !=
 536       static_cast<ssize_t> (reply_pickle.size()))
 537     PLOG(ERROR) << "write";
 538   return false;
 539 }
 540
 541 bool Zygote::HandleGetSandboxStatus(int fd,
 542                                     const Pickle& pickle,
 543                                     PickleIterator iter) {
 544   if (HANDLE_EINTR(write(fd, &sandbox_flags_, sizeof(sandbox_flags_))) !=
 545                    sizeof(sandbox_flags_)) {
 546     PLOG(ERROR) << "write";
 547   }
 548
 549   return false;
 550 }
 551
 552 }  // namespace content