From d6b8f17d493f73e29d89242b05a89827a790543e Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Tue, 20 Oct 2020 18:46:35 +0200
Subject: [PATCH] Disallow seeking on filtered streams

Most filters cannot deal with that, so we should disallow it.
---
 main/streams/streams.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/main/streams/streams.c b/main/streams/streams.c
index 1262c874f7e88..c24cb45796f55 100644
--- a/main/streams/streams.c
+++ b/main/streams/streams.c
@@ -1294,6 +1294,10 @@ PHPAPI zend_off_t _php_stream_tell(php_stream *stream)
 
 PHPAPI int _php_stream_seek(php_stream *stream, zend_off_t offset, int whence)
 {
+	if (php_stream_is_filtered(stream)) {
+		return -1;
+	}
+
 	if (stream->fclose_stdiocast == PHP_STREAM_FCLOSE_FOPENCOOKIE) {
 		/* flush to commit data written to the fopencookie FILE* */
 		fflush(stream->stdiocast);