Prevent ProcessProxy from passing bad fds to ProcessOutputWatcher

chromeos/process_proxy/process_output_watcher.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromeos/process_proxy/process_output_watcher.h"
 
 #include <sys/ioctl.h>
 #include <sys/select.h>
 #include <unistd.h>
 
@@ skipping 37 matching lines @@
     mask >>= 1;
     ++byte_count;
   }
   return byte_count ? byte_count : 1;
 }
 
 }  // namespace
 
 namespace chromeos {
 
+// static
+bool ProcessOutputWatcher::VerifyFileDescriptor(int fd) {
+  return (fd >= 0) && (fd < FD_SETSIZE);
+}
+
 ProcessOutputWatcher::ProcessOutputWatcher(
     int out_fd,
     int stop_fd,
     const ProcessOutputCallback& callback)
     : read_buffer_size_(0),
       out_fd_(out_fd),
       stop_fd_(stop_fd),
       on_read_callback_(callback) {
-  VerifyFileDescriptor(out_fd_);
-  VerifyFileDescriptor(stop_fd_);
+  CHECK(VerifyFileDescriptor(out_fd_));
+  CHECK(VerifyFileDescriptor(stop_fd_));
   max_fd_ = std::max(out_fd_, stop_fd_);
   // We want to be sure we will be able to add 0 at the end of the input, so -1.
   read_buffer_capacity_ = arraysize(read_buffer_) - 1;
 }
 
 void ProcessOutputWatcher::Start() {
   WatchProcessOutput();
   OnStop();
 }
 
@@ skipping 21 matching lines @@
     if (FD_ISSET(stop_fd_, &rfds)) {
       return;
     }
 
     if (out_fd_ != -1 && FD_ISSET(out_fd_, &rfds)) {
       ReadFromFd(PROCESS_OUTPUT_TYPE_OUT, &out_fd_);
     }
   }
 }
 
-void ProcessOutputWatcher::VerifyFileDescriptor(int fd) {
-  CHECK_LE(0, fd);
-  CHECK_GT(FD_SETSIZE, fd);
-}
-
 void ProcessOutputWatcher::ReadFromFd(ProcessOutputType type, int* fd) {
   // We don't want to necessary read pipe until it is empty so we don't starve
   // other streams in case data is written faster than we read it. If there is
   // more than read_buffer_size_ bytes in pipe, it will be read in the next
   // iteration.
   DCHECK_GT(read_buffer_capacity_, read_buffer_size_);
   ssize_t bytes_read =
       HANDLE_EINTR(read(*fd,
                         &read_buffer_[read_buffer_size_],
                         read_buffer_capacity_ - read_buffer_size_));
@@ skipping 65 matching lines @@
     }
   }
   read_buffer_size_ -= output_to_report;
 }
 
 void ProcessOutputWatcher::OnStop() {
   delete this;
 }
 
 }  // namespace chromeos