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Commit 4841e744 authored by Luis Hector Chavez's avatar Luis Hector Chavez
Browse files

debuggerd_handler: set PR_SET_PTRACER before running crash_dump. 

Set and restore PR_SET_PTRACER when performing a dump, so that when
Android is running on a kernel that has the Yama LSM enabled (and the
value of ptrace_scope is > 0), crash_dump can attach to processes and
print nice, symbolized stack traces.

Bug: 70992745
Test: kill -6 `pidof surfaceflinger` && logcat -d -b crash
      # in both sailfish and Chrome OS

Change-Id: If4646442c6000fdcc69cf4ab95fdc71ae74baaaf
parent 93d344d9

debuggerd/handler/debuggerd_handler.cpp

+16 −0
Original line number Diff line number Diff line
@@ -500,6 +500,17 @@ static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void* c 
    fatal_errno("failed to set dumpable");

  }



  // On kernels with yama_ptrace enabled, also allow any process to attach.

  bool restore_orig_ptracer = true;

  if (prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY) != 0) {

    if (errno == EINVAL) {

      // This kernel does not support PR_SET_PTRACER_ANY, or Yama is not enabled.

      restore_orig_ptracer = false;

    } else {

      fatal_errno("failed to set traceable");

    }

  }



  // Essentially pthread_create without CLONE_FILES, so we still work during file descriptor

  // exhaustion.

  pid_t child_pid =
@@ -521,6 +532,11 @@ static void debuggerd_signal_handler(int signal_number, siginfo_t* info, void* c 
    fatal_errno("failed to restore dumpable");

  }



  // Restore PR_SET_PTRACER to its original value.

  if (restore_orig_ptracer && prctl(PR_SET_PTRACER, 0) != 0) {

    fatal_errno("failed to restore traceable");

  }



  if (info->si_signo == DEBUGGER_SIGNAL) {

    // If the signal is fatal, don't unlock the mutex to prevent other crashing threads from

    // starting to dump right before our death.