Description:
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In zend_stream.cc the size passed to mmap is the size of the file + 
ZEND_MMAP_AHEAD.

*buf = mmap(0, size + ZEND_MMAP_AHEAD, PROT_READ, MAP_PRIVATE, 
fileno(file_handle->handle.fp), 0);

However, when munmap() is called the incorrect size is passed.

static void zend_stream_unmap(zend_stream *stream TSRMLS_DC) { /* {{{ */
#if HAVE_MMAP
        if (stream->mmap.map) {
                munmap(stream->mmap.map, stream->mmap.len);
        } else
#endif


The call to munmap should be

munmap(stream->mmap.map, stream->mmap.len + ZEND_MMAP_AHEAD);

Test script:
---------------
N/A

Expected result:
----------------
N/A

Actual result:
--------------
N/A