components/crash/browser/crash_handler_host_linux.cc

   1 // Copyright 2013 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 "components/crash/browser/crash_handler_host_linux.h"
   6
   7 #include <stdint.h>
   8 #include <stdlib.h>
   9 #include <sys/socket.h>
  10 #include <sys/syscall.h>
  11 #include <unistd.h>
  12
  13 #include "base/bind.h"
  14 #include "base/bind_helpers.h"
  15 #include "base/files/file_path.h"
  16 #include "base/files/file_util.h"
  17 #include "base/files/scoped_file.h"
  18 #include "base/format_macros.h"
  19 #include "base/linux_util.h"
  20 #include "base/logging.h"
  21 #include "base/message_loop/message_loop.h"
  22 #include "base/path_service.h"
  23 #include "base/posix/eintr_wrapper.h"
  24 #include "base/rand_util.h"
  25 #include "base/strings/string_util.h"
  26 #include "base/strings/stringprintf.h"
  27 #include "base/threading/thread.h"
  28 #include "breakpad/src/client/linux/handler/exception_handler.h"
  29 #include "breakpad/src/client/linux/minidump_writer/linux_dumper.h"
  30 #include "breakpad/src/client/linux/minidump_writer/minidump_writer.h"
  31 #include "components/crash/app/breakpad_linux_impl.h"
  32 #include "content/public/browser/browser_thread.h"
  33
  34 #if defined(OS_ANDROID) && !defined(__LP64__)
  35 #include <sys/linux-syscalls.h>
  36
  37 #define SYS_read __NR_read
  38 #endif
  39
  40 using content::BrowserThread;
  41 using google_breakpad::ExceptionHandler;
  42
  43 namespace breakpad {
  44
  45 namespace {
  46
  47 const size_t kNumFDs = 1;
  48 // The length of the control message:
  49 const size_t kControlMsgSize =
  50     CMSG_SPACE(kNumFDs * sizeof(int)) + CMSG_SPACE(sizeof(struct ucred));
  51 // The length of the regular payload:
  52 const size_t kCrashContextSize = sizeof(ExceptionHandler::CrashContext);
  53
  54 // Handles the crash dump and frees the allocated BreakpadInfo struct.
  55 void CrashDumpTask(CrashHandlerHostLinux* handler,
  56                    scoped_ptr<BreakpadInfo> info) {
  57   if (handler->IsShuttingDown() && info->upload) {
  58     base::DeleteFile(base::FilePath(info->filename), false);
  59 #if defined(ADDRESS_SANITIZER)
  60     base::DeleteFile(base::FilePath(info->log_filename), false);
  61 #endif
  62     return;
  63   }
  64
  65   HandleCrashDump(*info);
  66   delete[] info->filename;
  67 #if defined(ADDRESS_SANITIZER)
  68   delete[] info->log_filename;
  69   delete[] info->asan_report_str;
  70 #endif
  71   delete[] info->process_type;
  72   delete[] info->distro;
  73   delete info->crash_keys;
  74 }
  75
  76 }  // namespace
  77
  78 // Since instances of CrashHandlerHostLinux are leaked, they are only destroyed
  79 // at the end of the processes lifetime, which is greater in span than the
  80 // lifetime of the IO message loop. Thus, all calls to base::Bind() use
  81 // non-refcounted pointers.
  82
  83 CrashHandlerHostLinux::CrashHandlerHostLinux(const std::string& process_type,
  84                                              const base::FilePath& dumps_path,
  85                                              bool upload)
  86     : process_type_(process_type),
  87       dumps_path_(dumps_path),
  88       upload_(upload),
  89       shutting_down_(false),
  90       worker_pool_token_(BrowserThread::GetBlockingPool()->GetSequenceToken()) {
  91   int fds[2];
  92   // We use SOCK_SEQPACKET rather than SOCK_DGRAM to prevent the process from
  93   // sending datagrams to other sockets on the system. The sandbox may prevent
  94   // the process from calling socket() to create new sockets, but it'll still
  95   // inherit some sockets. With PF_UNIX+SOCK_DGRAM, it can call sendmsg to send
  96   // a datagram to any (abstract) socket on the same system. With
  97   // SOCK_SEQPACKET, this is prevented.
  98   CHECK_EQ(0, socketpair(AF_UNIX, SOCK_SEQPACKET, 0, fds));
  99   static const int on = 1;
 100
 101   // Enable passcred on the server end of the socket
 102   CHECK_EQ(0, setsockopt(fds[1], SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)));
 103
 104   process_socket_ = fds[0];
 105   browser_socket_ = fds[1];
 106
 107   BrowserThread::PostTask(
 108       BrowserThread::IO, FROM_HERE,
 109       base::Bind(&CrashHandlerHostLinux::Init, base::Unretained(this)));
 110 }
 111
 112 CrashHandlerHostLinux::~CrashHandlerHostLinux() {
 113   close(process_socket_);
 114   close(browser_socket_);
 115 }
 116
 117 void CrashHandlerHostLinux::StartUploaderThread() {
 118   uploader_thread_.reset(
 119       new base::Thread(process_type_ + "_crash_uploader"));
 120   uploader_thread_->Start();
 121 }
 122
 123 void CrashHandlerHostLinux::Init() {
 124   base::MessageLoopForIO* ml = base::MessageLoopForIO::current();
 125   CHECK(ml->WatchFileDescriptor(
 126       browser_socket_, true /* persistent */,
 127       base::MessageLoopForIO::WATCH_READ,
 128       &file_descriptor_watcher_, this));
 129   ml->AddDestructionObserver(this);
 130 }
 131
 132 void CrashHandlerHostLinux::OnFileCanWriteWithoutBlocking(int fd) {
 133   NOTREACHED();
 134 }
 135
 136 void CrashHandlerHostLinux::OnFileCanReadWithoutBlocking(int fd) {
 137   DCHECK_EQ(browser_socket_, fd);
 138
 139   // A process has crashed and has signaled us by writing a datagram
 140   // to the death signal socket. The datagram contains the crash context needed
 141   // for writing the minidump as well as a file descriptor and a credentials
 142   // block so that they can't lie about their pid.
 143   //
 144   // The message sender is in components/crash/app/breakpad_linux.cc.
 145
 146   struct msghdr msg = {0};
 147   struct iovec iov[kCrashIovSize];
 148
 149   scoped_ptr<char[]> crash_context(new char[kCrashContextSize]);
 150 #if defined(ADDRESS_SANITIZER)
 151   scoped_ptr<char[]> asan_report(new char[kMaxAsanReportSize + 1]);
 152 #endif
 153
 154   scoped_ptr<CrashKeyStorage> crash_keys(new CrashKeyStorage);
 155   google_breakpad::SerializedNonAllocatingMap* serialized_crash_keys;
 156   size_t crash_keys_size = crash_keys->Serialize(
 157       const_cast<const google_breakpad::SerializedNonAllocatingMap**>(
 158           &serialized_crash_keys));
 159
 160   char* tid_buf_addr = NULL;
 161   int tid_fd = -1;
 162   uint64_t uptime;
 163   size_t oom_size;
 164   char control[kControlMsgSize];
 165   const ssize_t expected_msg_size =
 166       kCrashContextSize +
 167       sizeof(tid_buf_addr) + sizeof(tid_fd) +
 168       sizeof(uptime) +
 169 #if defined(ADDRESS_SANITIZER)
 170       kMaxAsanReportSize + 1 +
 171 #endif
 172       sizeof(oom_size) +
 173       crash_keys_size;
 174   iov[0].iov_base = crash_context.get();
 175   iov[0].iov_len = kCrashContextSize;
 176   iov[1].iov_base = &tid_buf_addr;
 177   iov[1].iov_len = sizeof(tid_buf_addr);
 178   iov[2].iov_base = &tid_fd;
 179   iov[2].iov_len = sizeof(tid_fd);
 180   iov[3].iov_base = &uptime;
 181   iov[3].iov_len = sizeof(uptime);
 182   iov[4].iov_base = &oom_size;
 183   iov[4].iov_len = sizeof(oom_size);
 184   iov[5].iov_base = serialized_crash_keys;
 185   iov[5].iov_len = crash_keys_size;
 186 #if !defined(ADDRESS_SANITIZER)
 187   static_assert(5 == kCrashIovSize - 1, "kCrashIovSize should equal 6");
 188 #else
 189   iov[6].iov_base = asan_report.get();
 190   iov[6].iov_len = kMaxAsanReportSize + 1;
 191   static_assert(6 == kCrashIovSize - 1, "kCrashIovSize should equal 7");
 192 #endif
 193   msg.msg_iov = iov;
 194   msg.msg_iovlen = kCrashIovSize;
 195   msg.msg_control = control;
 196   msg.msg_controllen = kControlMsgSize;
 197
 198   const ssize_t msg_size = HANDLE_EINTR(recvmsg(browser_socket_, &msg, 0));
 199   if (msg_size < 0) {
 200     LOG(ERROR) << "Error reading from death signal socket. Crash dumping"
 201                << " is disabled."
 202                << " msg_size:" << msg_size
 203                << " errno:" << errno;
 204     file_descriptor_watcher_.StopWatchingFileDescriptor();
 205     return;
 206   }
 207   const bool bad_message = (msg_size != expected_msg_size ||
 208                             msg.msg_controllen != kControlMsgSize ||
 209                             msg.msg_flags & ~MSG_TRUNC);
 210   base::ScopedFD signal_fd;
 211   pid_t crashing_pid = -1;
 212   if (msg.msg_controllen > 0) {
 213     // Walk the control payload and extract the file descriptor and
 214     // validated pid.
 215     for (struct cmsghdr *hdr = CMSG_FIRSTHDR(&msg); hdr;
 216          hdr = CMSG_NXTHDR(&msg, hdr)) {
 217       if (hdr->cmsg_level != SOL_SOCKET)
 218         continue;
 219       if (hdr->cmsg_type == SCM_RIGHTS) {
 220         const size_t len = hdr->cmsg_len -
 221             (((uint8_t*)CMSG_DATA(hdr)) - (uint8_t*)hdr);
 222         DCHECK_EQ(0U, len % sizeof(int));
 223         const size_t num_fds = len / sizeof(int);
 224         if (num_fds != kNumFDs) {
 225           // A nasty process could try and send us too many descriptors and
 226           // force a leak.
 227           LOG(ERROR) << "Death signal contained wrong number of descriptors;"
 228                      << " num_fds:" << num_fds;
 229           for (size_t i = 0; i < num_fds; ++i)
 230             close(reinterpret_cast<int*>(CMSG_DATA(hdr))[i]);
 231           return;
 232         }
 233         DCHECK(!signal_fd.is_valid());
 234         int fd = reinterpret_cast<int*>(CMSG_DATA(hdr))[0];
 235         DCHECK_GE(fd, 0);  // The kernel should never send a negative fd.
 236         signal_fd.reset(fd);
 237       } else if (hdr->cmsg_type == SCM_CREDENTIALS) {
 238         DCHECK_EQ(-1, crashing_pid);
 239         const struct ucred *cred =
 240             reinterpret_cast<struct ucred*>(CMSG_DATA(hdr));
 241         crashing_pid = cred->pid;
 242       }
 243     }
 244   }
 245
 246   if (bad_message) {
 247     LOG(ERROR) << "Received death signal message with the wrong size;"
 248                << " msg.msg_controllen:" << msg.msg_controllen
 249                << " msg.msg_flags:" << msg.msg_flags
 250                << " kCrashContextSize:" << kCrashContextSize
 251                << " kControlMsgSize:" << kControlMsgSize;
 252     return;
 253   }
 254   if (crashing_pid == -1 || !signal_fd.is_valid()) {
 255     LOG(ERROR) << "Death signal message didn't contain all expected control"
 256                << " messages";
 257     return;
 258   }
 259
 260   // The crashing TID set inside the compromised context via
 261   // sys_gettid() in ExceptionHandler::HandleSignal might be wrong (if
 262   // the kernel supports PID namespacing) and may need to be
 263   // translated.
 264   //
 265   // We expect the crashing thread to be in sys_read(), waiting for us to
 266   // write to |signal_fd|. Most newer kernels where we have the different pid
 267   // namespaces also have /proc/[pid]/syscall, so we can look through
 268   // |actual_crashing_pid|'s thread group and find the thread that's in the
 269   // read syscall with the right arguments.
 270
 271   std::string expected_syscall_data;
 272   // /proc/[pid]/syscall is formatted as follows:
 273   // syscall_number arg1 ... arg6 sp pc
 274   // but we just check syscall_number through arg3.
 275   base::StringAppendF(&expected_syscall_data, "%d 0x%x %p 0x1 ",
 276                       SYS_read, tid_fd, tid_buf_addr);
 277   bool syscall_supported = false;
 278   pid_t crashing_tid =
 279       base::FindThreadIDWithSyscall(crashing_pid,
 280                                     expected_syscall_data,
 281                                     &syscall_supported);
 282   if (crashing_tid == -1) {
 283     // We didn't find the thread we want. Maybe it didn't reach
 284     // sys_read() yet or the thread went away.  We'll just take a
 285     // guess here and assume the crashing thread is the thread group
 286     // leader.  If procfs syscall is not supported by the kernel, then
 287     // we assume the kernel also does not support TID namespacing and
 288     // trust the TID passed by the crashing process.
 289     LOG(WARNING) << "Could not translate tid - assuming crashing thread is "
 290         "thread group leader; syscall_supported=" << syscall_supported;
 291     crashing_tid = crashing_pid;
 292   }
 293
 294   ExceptionHandler::CrashContext* bad_context =
 295       reinterpret_cast<ExceptionHandler::CrashContext*>(crash_context.get());
 296   bad_context->tid = crashing_tid;
 297
 298   scoped_ptr<BreakpadInfo> info(new BreakpadInfo);
 299
 300   info->fd = -1;
 301   info->process_type_length = process_type_.length();
 302   // Freed in CrashDumpTask().
 303   char* process_type_str = new char[info->process_type_length + 1];
 304   process_type_.copy(process_type_str, info->process_type_length);
 305   process_type_str[info->process_type_length] = '\0';
 306   info->process_type = process_type_str;
 307
 308   // Memory released from scoped_ptrs below are also freed in CrashDumpTask().
 309   info->crash_keys = crash_keys.release();
 310 #if defined(ADDRESS_SANITIZER)
 311   asan_report[kMaxAsanReportSize] = '\0';
 312   info->asan_report_str = asan_report.release();
 313   info->asan_report_length = strlen(info->asan_report_str);
 314 #endif
 315
 316   info->process_start_time = uptime;
 317   info->oom_size = oom_size;
 318 #if defined(OS_ANDROID)
 319   // Nothing gets uploaded in android.
 320   info->upload = false;
 321 #else
 322   info->upload = upload_;
 323 #endif
 324
 325
 326   BrowserThread::GetBlockingPool()->PostSequencedWorkerTask(
 327       worker_pool_token_,
 328       FROM_HERE,
 329       base::Bind(&CrashHandlerHostLinux::WriteDumpFile,
 330                  base::Unretained(this),
 331                  base::Passed(&info),
 332                  base::Passed(&crash_context),
 333                  crashing_pid,
 334                  signal_fd.release()));
 335 }
 336
 337 void CrashHandlerHostLinux::WriteDumpFile(scoped_ptr<BreakpadInfo> info,
 338                                           scoped_ptr<char[]> crash_context,
 339                                           pid_t crashing_pid,
 340                                           int signal_fd) {
 341   DCHECK(BrowserThread::GetBlockingPool()->IsRunningSequenceOnCurrentThread(
 342       worker_pool_token_));
 343
 344   // Set |info->distro| here because base::GetLinuxDistro() needs to run on a
 345   // blocking thread.
 346   std::string distro = base::GetLinuxDistro();
 347   info->distro_length = distro.length();
 348   // Freed in CrashDumpTask().
 349   char* distro_str = new char[info->distro_length + 1];
 350   distro.copy(distro_str, info->distro_length);
 351   distro_str[info->distro_length] = '\0';
 352   info->distro = distro_str;
 353
 354   base::FilePath dumps_path("/tmp");
 355   PathService::Get(base::DIR_TEMP, &dumps_path);
 356   if (!info->upload)
 357     dumps_path = dumps_path_;
 358   const std::string minidump_filename =
 359       base::StringPrintf("%s/chromium-%s-minidump-%016" PRIx64 ".dmp",
 360                          dumps_path.value().c_str(),
 361                          process_type_.c_str(),
 362                          base::RandUint64());
 363
 364   if (!google_breakpad::WriteMinidump(minidump_filename.c_str(),
 365                                       kMaxMinidumpFileSize,
 366                                       crashing_pid,
 367                                       crash_context.get(),
 368                                       kCrashContextSize,
 369                                       google_breakpad::MappingList(),
 370                                       google_breakpad::AppMemoryList())) {
 371     LOG(ERROR) << "Failed to write crash dump for pid " << crashing_pid;
 372   }
 373 #if defined(ADDRESS_SANITIZER)
 374   // Create a temporary file holding the AddressSanitizer report.
 375   const base::FilePath log_path =
 376       base::FilePath(minidump_filename).ReplaceExtension("log");
 377   base::WriteFile(log_path, info->asan_report_str, info->asan_report_length);
 378 #endif
 379
 380   // Freed in CrashDumpTask().
 381   char* minidump_filename_str = new char[minidump_filename.length() + 1];
 382   minidump_filename.copy(minidump_filename_str, minidump_filename.length());
 383   minidump_filename_str[minidump_filename.length()] = '\0';
 384   info->filename = minidump_filename_str;
 385 #if defined(ADDRESS_SANITIZER)
 386   // Freed in CrashDumpTask().
 387   char* minidump_log_filename_str = new char[minidump_filename.length() + 1];
 388   minidump_filename.copy(minidump_log_filename_str, minidump_filename.length());
 389   memcpy(minidump_log_filename_str + minidump_filename.length() - 3, "log", 3);
 390   minidump_log_filename_str[minidump_filename.length()] = '\0';
 391   info->log_filename = minidump_log_filename_str;
 392 #endif
 393   info->pid = crashing_pid;
 394
 395   BrowserThread::PostTask(
 396       BrowserThread::IO, FROM_HERE,
 397       base::Bind(&CrashHandlerHostLinux::QueueCrashDumpTask,
 398                  base::Unretained(this),
 399                  base::Passed(&info),
 400                  signal_fd));
 401 }
 402
 403 void CrashHandlerHostLinux::QueueCrashDumpTask(scoped_ptr<BreakpadInfo> info,
 404                                                int signal_fd) {
 405   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 406
 407   // Send the done signal to the process: it can exit now.
 408   struct msghdr msg = {0};
 409   struct iovec done_iov;
 410   done_iov.iov_base = const_cast<char*>("\x42");
 411   done_iov.iov_len = 1;
 412   msg.msg_iov = &done_iov;
 413   msg.msg_iovlen = 1;
 414
 415   HANDLE_EINTR(sendmsg(signal_fd, &msg, MSG_DONTWAIT | MSG_NOSIGNAL));
 416   close(signal_fd);
 417
 418   uploader_thread_->message_loop()->PostTask(
 419       FROM_HERE,
 420       base::Bind(&CrashDumpTask, base::Unretained(this), base::Passed(&info)));
 421 }
 422
 423 void CrashHandlerHostLinux::WillDestroyCurrentMessageLoop() {
 424   file_descriptor_watcher_.StopWatchingFileDescriptor();
 425
 426   // If we are quitting and there are crash dumps in the queue, turn them into
 427   // no-ops.
 428   shutting_down_ = true;
 429   uploader_thread_->Stop();
 430 }
 431
 432 bool CrashHandlerHostLinux::IsShuttingDown() const {
 433   return shutting_down_;
 434 }
 435
 436 }  // namespace breakpad