Fix OSS-Fuzz #385993744

ext/standard/tests/filters/oss_fuzz_385993744.phpt

@@ -0,0 +1,28 @@
+--TEST--
+OSS-Fuzz #385993744
+--FILE--
+<?php
+
+class SampleFilter extends php_user_filter
+{
+    private $data = '';
+
+    public function filter($in, $out, &$consumed, $closing): int
+    {
+        while ($bucket = stream_bucket_make_writeable($in))
+        {
+            $this->data .= $bucket->data;
+        }
+
+        $bucket = stream_bucket_new($this->stream, $this->data);
+        stream_bucket_append($out, $bucket);
+
+        return PSFS_FEED_ME;
+    }
+}
+stream_filter_register('sample.filter', SampleFilter::class);
+var_dump(file_get_contents('php://filter/read=sample.filter/resource='. __FILE__));
+
+?>
+--EXPECT--
+string(0) ""

main/streams/filter.c

@@ -354,6 +354,13 @@ PHPAPI int php_stream_filter_append_ex(php_stream_filter_chain *chain, php_strea
 				   Reset stream's internal read buffer since the filter is "holding" it. */
 				stream->readpos = 0;
 				stream->writepos = 0;
+
+				/* Filter could have added buckets anyway, but signalled that it did not return any. Discard them. */
+				while (brig_out.head) {
+					bucket = brig_out.head;
+					php_stream_bucket_unlink(bucket);
+					php_stream_bucket_delref(bucket);
+				}
 				break;
 			case PSFS_PASS_ON:
 				/* If any data is consumed, we cannot rely upon the existing read buffer,

main/streams/streams.c

@@ -630,6 +630,12 @@ PHPAPI zend_result _php_stream_fill_read_buffer(php_stream *stream, size_t size)
 					/* when a filter needs feeding, there is no brig_out to deal with.
 					 * we simply continue the loop; if the caller needs more data,
 					 * we will read again, otherwise out job is done here */
+
+					/* Filter could have added buckets anyway, but signalled that it did not return any. Discard them. */
+					while ((bucket = brig_outp->head)) {
+						php_stream_bucket_unlink(bucket);
+						php_stream_bucket_delref(bucket);
+					}
 					break;
 
 				case PSFS_ERR_FATAL:
@@ -1263,14 +1269,22 @@ static ssize_t _php_stream_write_filtered(php_stream *stream, const char *buf, s
 				php_stream_bucket_delref(bucket);
 			}
 			break;
-		case PSFS_FEED_ME:
-			/* need more data before we can push data through to the stream */
-			break;
 
 		case PSFS_ERR_FATAL:
 			/* some fatal error.  Theoretically, the stream is borked, so all
 			 * further writes should fail. */
-			return (ssize_t) -1;
+			consumed = (ssize_t) -1;
+			ZEND_FALLTHROUGH;
+
+		case PSFS_FEED_ME:
+			/* need more data before we can push data through to the stream */
+			/* Filter could have added buckets anyway, but signalled that it did not return any. Discard them. */
+			while (brig_inp->head) {
+				bucket = brig_inp->head;
+				php_stream_bucket_unlink(bucket);
+				php_stream_bucket_delref(bucket);
+			}
+			break;
 	}
 
 	return consumed;