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Commit 2a18b822 authored by Josh Gao's avatar Josh Gao
Browse files

crash_dump: remove unneeded/faulty checks. 

We already check our /proc/`getppid()` fd every time we attach a thread, so
these were unneeded at best. The one that happened after dropping
capabilities was actively wrong, though, because /proc/pid access
checks happen on every operation. (only on some kernels?)

Also, add a check that getppid() doesn't change after opening
/proc/getppid().

Bug: http://b/35241370
Test: debuggerd -b `pidof com.android.bluetooth`
Change-Id: I807439d8c2afd027f3c382face50167a8a7946c4
parent 325eeebc

debuggerd/crash_dump.cpp

+5 −14
Original line number Diff line number Diff line
@@ -219,17 +219,6 @@ static void drop_capabilities() { 
  }

}



static void check_process(int proc_fd, pid_t expected_pid) {

  android::procinfo::ProcessInfo proc_info;

  if (!android::procinfo::GetProcessInfoFromProcPidFd(proc_fd, &proc_info)) {

    LOG(FATAL) << "failed to fetch process info";

  }



  if (proc_info.pid != expected_pid) {

    LOG(FATAL) << "pid mismatch: expected " << expected_pid << ", actual " << proc_info.pid;

  }

}



int main(int argc, char** argv) {

  pid_t target = getppid();

  bool tombstoned_connected = false;
@@ -282,6 +271,11 @@ int main(int argc, char** argv) { 
    PLOG(FATAL) << "failed to open " << target_proc_path;

  }



  // Make sure our parent didn't die.

  if (getppid() != target) {

    PLOG(FATAL) << "parent died";

  }



  // Reparent ourselves to init, so that the signal handler can waitpid on the

  // original process to avoid leaving a zombie for non-fatal dumps.

  pid_t forkpid = fork();
@@ -294,8 +288,6 @@ int main(int argc, char** argv) { 
  // Die if we take too long.

  alarm(20);



  check_process(target_proc_fd, target);



  std::string attach_error;



  // Seize the main thread.
@@ -337,7 +329,6 @@ int main(int argc, char** argv) { 


  // Drop our capabilities now that we've attached to the threads we care about.

  drop_capabilities();

  check_process(target_proc_fd, target);



  LOG(INFO) << "obtaining output fd from tombstoned";

  tombstoned_connected = tombstoned_connect(target, &tombstoned_socket, &output_fd);