From: Timo Sirainen <timo.sirainen@dovecot.fi>
Date: Sun, 10 Dec 2017 18:00:21 +0000 (+0200)
Subject: lib-test: istream-test - Don't modify existing snapshots' memareas
X-Git-Tag: 2.3.0.rc1~155
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=21138be4989503314641025ab07a7010a380a159;p=thirdparty%2Fdovecot%2Fcore.git

lib-test: istream-test - Don't modify existing snapshots' memareas

At least with --enable-devel-checks this caused istream-sized unit test to
randomly panic:

Panic: file istream.c: line 279 (i_stream_read): assertion failed: (memcmp(prev_buf, prev_data + prev_skip, prev_pos - prev_skip) == 0)
---

diff --git a/src/lib-test/test-istream.c b/src/lib-test/test-istream.c
index 84f06b1b65..1c3efcf58a 100644
--- a/src/lib-test/test-istream.c
+++ b/src/lib-test/test-istream.c
@@ -52,9 +52,15 @@ static ssize_t test_read(struct istream_private *stream)
 		    cur_max > stream->skip + stream->max_buffer_size)
 			cur_max = stream->skip + stream->max_buffer_size;
 
-		/* use exactly correct buffer size so valgrind can catch
-		   read overflows */
-		if (stream->buffer_size != cur_max && cur_max > 0) {
+		/* Reallocate the memory area if needed. Use exactly correct
+		   buffer size so valgrind can catch read overflows. If a
+		   correctly sized memarea already exists, use it only if
+		   its refcount is 1. Otherwise with refcount>1 we could be
+		   moving data within an existing memarea, which breaks
+		   snapshots. */
+		if (cur_max > 0 && (stream->buffer_size != cur_max ||
+				    stream->memarea == NULL ||
+				    memarea_get_refcount(stream->memarea) > 1)) {
 			void *old_w_buffer = stream->w_buffer;
 			stream->w_buffer = i_malloc(cur_max);
 			memcpy(stream->w_buffer, old_w_buffer,