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Commit c954ec09 authored by Josh Gao's avatar Josh Gao
Browse files

debuggerd_handler: use syscall(__NR_close) instead of close. 

Avoid bionic's file descriptor ownership checks by calling the close
syscall manually.

Test: debuggerd_test
Change-Id: I10af6aca0e66fe030fd7a53506ae61c87695641d
parent fcf2c01b

base/include/android-base/unique_fd.h

+7 −3
Original line number Diff line number Diff line
@@ -151,7 +151,8 @@ using unique_fd = unique_fd_impl<DefaultCloser>; 
#if !defined(_WIN32)



// Inline functions, so that they can be used header-only.

inline bool Pipe(unique_fd* read, unique_fd* write) {

template <typename Closer>

inline bool Pipe(unique_fd_impl<Closer>* read, unique_fd_impl<Closer>* write) {

  int pipefd[2];



#if defined(__linux__)
@@ -175,7 +176,9 @@ inline bool Pipe(unique_fd* read, unique_fd* write) { 
  return true;

}



inline bool Socketpair(int domain, int type, int protocol, unique_fd* left, unique_fd* right) {

template <typename Closer>

inline bool Socketpair(int domain, int type, int protocol, unique_fd_impl<Closer>* left,

                       unique_fd_impl<Closer>* right) {

  int sockfd[2];

  if (socketpair(domain, type, protocol, sockfd) != 0) {

    return false;
@@ -185,7 +188,8 @@ inline bool Socketpair(int domain, int type, int protocol, unique_fd* left, uniq 
  return true;

}



inline bool Socketpair(int type, unique_fd* left, unique_fd* right) {

template <typename Closer>

inline bool Socketpair(int type, unique_fd_impl<Closer>* left, unique_fd_impl<Closer>* right) {

  return Socketpair(AF_UNIX, type, 0, left, right);

}

debuggerd/handler/debuggerd_handler.cpp

+12 −2
Original line number Diff line number Diff line
@@ -59,7 +59,16 @@ 
#include "protocol.h"



using android::base::Pipe;

using android::base::unique_fd;



// We muck with our fds in a 'thread' that doesn't share the same fd table.

// Close fds in that thread with a raw close syscall instead of going through libc.

struct FdsanBypassCloser {

  static void Close(int fd) {

    syscall(__NR_close, fd);

  }

};



using unique_fd = android::base::unique_fd_impl<FdsanBypassCloser>;



// see man(2) prctl, specifically the section about PR_GET_NAME

#define MAX_TASK_NAME_LEN (16)
@@ -299,7 +308,8 @@ static int debuggerd_dispatch_pseudothread(void* arg) { 
  debugger_thread_info* thread_info = static_cast<debugger_thread_info*>(arg);



  for (int i = 0; i < 1024; ++i) {

    close(i);

    // Don't use close to avoid bionic's file descriptor ownership checks.

    syscall(__NR_close, i);

  }



  int devnull = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));