linux: Crash browser on too-big messages to zygote.

base/posix/unix_domain_socket.h

 // Copyright (c) 2011 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.
 
 #ifndef BASE_POSIX_UNIX_DOMAIN_SOCKET_H_
 #define BASE_POSIX_UNIX_DOMAIN_SOCKET_H_
 
 #include <stdint.h>
 #include <sys/types.h>
 #include <vector>
 
 #include "base/base_export.h"
 
 class Pickle;
 
 class BASE_EXPORT UnixDomainSocket {
  public:
+  // Maximum number of file descriptors that can be read by RecvMsg().
+  static const size_t kMaxFileDescriptors;
+
   // Use sendmsg to write the given msg and include a vector of file
   // descriptors. Returns true if successful.
   static bool SendMsg(int fd,
                       const void* msg,
                       size_t length,
                       const std::vector<int>& fds);
 
   // Use recvmsg to read a message and an array of file descriptors. Returns
-  // -1 on failure. Note: will read, at most, 16 descriptors.
+  // -1 on failure. Note: will read, at most, |kMaxFileDescriptors| descriptors.
   static ssize_t RecvMsg(int fd,
                          void* msg,
                          size_t length,
                          std::vector<int>* fds);
 
   // Perform a sendmsg/recvmsg pair.
   //   1. This process creates a UNIX DGRAM socketpair.
   //   2. This proces writes a request to |fd| with an SCM_RIGHTS control
   //      message containing on end of the fresh socket pair.
   //   3. This process blocks reading from the other end of the fresh
   //      socketpair.
   //   4. The target process receives the request, processes it and writes the
   //      reply to the end of the socketpair contained in the request.
   //   5. This process wakes up and continues.
   //
   //   fd: descriptor to send the request on
   //   reply: buffer for the reply
   //   reply_len: size of |reply|
   //   result_fd: (may be NULL) the file descriptor returned in the reply
   //              (if any)
   //   request: the bytes to send in the request
   static ssize_t SendRecvMsg(int fd,
                              uint8_t* reply,
                              unsigned reply_len,
                              int* result_fd,
                              const Pickle& request);
 };
 
 #endif  // BASE_POSIX_UNIX_DOMAIN_SOCKET_POSIX_H_