Check read() result in std::random_device.

	PR libstdc++/65142
	* src/c++11/random.cc (random_device::_M_getval()): Check read result.

From-SVN: r227687

libstdc++-v3/ChangeLog

+2015-09-11  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/65142
+	* src/c++11/random.cc (random_device::_M_getval()): Check read result.
+
 2015-09-11  John Marino  <gnugcc@marino.st>
 	    Jonathan Wakely  <jwakely@redhat.com>
 

libstdc++-v3/src/c++11/random.cc

@@ -130,13 +130,17 @@ namespace std _GLIBCXX_VISIBILITY(default)
 #endif
 
     result_type __ret;
+
 #ifdef _GLIBCXX_HAVE_UNISTD_H
-    read(fileno(static_cast<FILE*>(_M_file)),
+    auto e = read(fileno(static_cast<FILE*>(_M_file)),
 		  static_cast<void*>(&__ret), sizeof(result_type));
 #else
-    std::fread(static_cast<void*>(&__ret), sizeof(result_type),
+    auto e = std::fread(static_cast<void*>(&__ret), sizeof(result_type),
 		        1, static_cast<FILE*>(_M_file));
 #endif
+    if (e != sizeof(result_type))
+      __throw_runtime_error(__N("random_device could not read enough bytes"));
+
     return __ret;
   }