Fix #80384: limit read buffer size

In the case of a stream with no filters, php_stream_fill_read_buffer
only reads stream->chunk_size into the read buffer. If the stream has
filters attached, it could unnecessarily buffer a large amount of data.

With this change, php_stream_fill_read_buffer only proceeds until either
the requested size or stream->chunk_size is available in the read buffer.

Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>

Closes GH-6444.

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/basic/bug80384.phpt b/tests/basic/bug80384.phpt
new file mode 100644
index 0000000000..cf30e8601b
--- /dev/null
+++ b/tests/basic/bug80384.phpt
@@ -0,0 +1,28 @@
+--TEST--
+Bug #80384 large reads cause filters to internally buffer large amounts of memory
+--FILE--
+<?php
+/* First, create a file to read */
+$tmp_filename = __DIR__ . "/bug80384.tmp";
+$fp = fopen($tmp_filename, 'w');
+for ($i=0; $i<1024; $i++) {
+    fwrite($fp, str_repeat('ABCDEFGH', 1024));
+}
+fclose($fp);
+
+/* Stream the file through a filter */
+$fp = fopen($tmp_filename, 'r');
+$filter = stream_filter_append($fp, "string.rot13");
+
+$mem_start = memory_get_usage();
+fread($fp, 8 * 1024 * 1024);
+$mem_final = memory_get_usage();
+fclose($fp);
+var_dump($mem_final - $mem_start < 32768);
+?>
+--CLEAN--
+<?php
+unlink(__DIR__ . "/bug80384.tmp");
+?>
+--EXPECT--
+bool(true)