[NaCl SDK] nacl_io: Fix dlopen'ing a file not in the .nmf

native_client_sdk/src/libraries/nacl_io/mount_node.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 "nacl_io/mount_node.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
 #include <sys/stat.h>
@@ skipping 62 matching lines @@
   return -1;
 }
 
 int MountNode::Write(size_t offs, const void* buf, size_t count) {
   errno = EINVAL;
   return -1;
 }
 
 void* MountNode::MMap(void* addr, size_t length, int prot, int flags,
                       size_t offset) {
+  // Never allow mmap'ing PROT_EXEC. The passthrough node supports this, but we
+  // don't. Fortunately, glibc will fallback if this fails, so dlopen will
+  // continue to work.
+  if (prot & PROT_EXEC) {
+    errno = EPERM;
+    return MAP_FAILED;
+  }
+
   // This default mmap support is just enough to make dlopen work.
   // This implementation just reads from the mount into the mmap'd memory area.
   void* new_addr = addr;
   int err = _real_mmap(&new_addr, length, prot | PROT_WRITE, flags |
                        MAP_ANONYMOUS, -1, 0);
   if (new_addr == MAP_FAILED) {
     _real_munmap(new_addr, length);
     errno = err;
     return MAP_FAILED;
   }
@@ skipping 63 matching lines @@
 
 void MountNode::Link() {
   Acquire();
   stat_.st_nlink++;
 }
 
 void MountNode::Unlink() {
   stat_.st_nlink--;
   Release();
 }