From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Mon, 15 Jun 2020 07:33:53 +0000 (+0300)
Subject: lib-storage: istream-mail - Fix assert-crash on handling corrupted mail size
X-Git-Tag: 2.3.13~509
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8a31ae84adc012e09c593f35edd3c7be34b67cbb;p=thirdparty%2Fdovecot%2Fcore.git

lib-storage: istream-mail - Fix assert-crash on handling corrupted mail size

In some situations the "Cached message size smaller than expected" error
handling could have resulted in:

Panic: file istream.c: line 315 (i_stream_read_memarea): assertion failed: (old_size <= _stream->pos - _stream->skip)
---

diff --git a/src/lib-storage/index/istream-mail.c b/src/lib-storage/index/istream-mail.c
index 365f8c897e..3cb3571479 100644
--- a/src/lib-storage/index/istream-mail.c
+++ b/src/lib-storage/index/istream-mail.c
@@ -124,7 +124,8 @@ i_stream_mail_read(struct istream_private *stream)
 			i_stream_mail_set_size_corrupted(mstream, size);
 			/* istream code expects that the position has not changed
 			   when read error occurs, so move pos back. */
-			stream->pos -= size;
+			i_assert(stream->pos >= (size_t)ret);
+			stream->pos -= ret;
 			return -1;
 		}
 	} else if (ret == -1 && stream->istream.eof) {