Fixed bug #78902

Author: liudaixiao

NEWS

@@ -29,6 +29,9 @@ PHP                                                                        NEWS
   . Fixed bug #79151 (heap use after free caused by
     spl_dllist_it_helper_move_forward). (Nikita)
 
+- Standard:
+  . Fixed bug #78902 (Memory leak when using stream_filter_append). (liudaixiao)
+
 23 Jan 2020, PHP 7.3.14
 
 - Core

ext/standard/tests/streams/bug78902.phpt

@@ -1,7 +1,5 @@
 --TEST--
 Bug #78902: Memory leak when using stream_filter_append
---XFAIL--
-This bug was introduced in PHP 7.3.11 an is still open
 --INI--
 memory_limit=512k
 --FILE--

main/streams/streams.c

@@ -577,8 +577,15 @@ PHPAPI void _php_stream_fill_read_buffer(php_stream *stream, size_t size)
 					 * stream read buffer */
 					while (brig_inp->head) {
 						bucket = brig_inp->head;
-						/* grow buffer to hold this bucket
-						 * TODO: this can fail for persistent streams */
+						/* reduce buffer memory consumption if possible, to avoid a realloc */
+						if (stream->readbuf && stream->readbuflen - stream->writepos < bucket->buflen) {
+							if (stream->writepos > stream->readpos) {
+								memmove(stream->readbuf, stream->readbuf + stream->readpos, stream->writepos - stream->readpos);
+							}
+							stream->writepos -= stream->readpos;
+							stream->readpos = 0;
+						}
+						/* grow buffer to hold this bucket */
 						if (stream->readbuflen - stream->writepos < bucket->buflen) {
 							stream->readbuflen += bucket->buflen;
 							stream->readbuf = perealloc(stream->readbuf, stream->readbuflen,