From: Aki Tuomi <aki.tuomi@open-xchange.com>
Date: Wed, 26 Feb 2020 10:57:06 +0000 (+0200)
Subject: lib-compression: istream-lz4 - Refactor how chunk header is read
X-Git-Tag: 2.3.11.2~566
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e7f738c5324b422e6fe0eaea51b20bb7cb622535;p=thirdparty%2Fdovecot%2Fcore.git

lib-compression: istream-lz4 - Refactor how chunk header is read

Chunk headers can sometime be at read borders. In this case more
data needs to be read. Fixes

Panic: file istream.c: line 333 (i_stream_read_memarea): assertion failed: (!stream->blocking)
---

diff --git a/src/lib-compression/istream-lz4.c b/src/lib-compression/istream-lz4.c
index b7100ec6e6..53f7947679 100644
--- a/src/lib-compression/istream-lz4.c
+++ b/src/lib-compression/istream-lz4.c
@@ -85,6 +85,46 @@ static int i_stream_lz4_read_header(struct lz4_istream *zstream)
 	return 1;
 }
 
+static int i_stream_lz4_read_chunk_header(struct lz4_istream *zstream)
+{
+	int ret;
+	size_t size;
+	const unsigned char *data;
+	struct istream_private *stream = &zstream->istream;
+
+	i_assert(zstream->chunk_buf->used <= IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
+	ret = i_stream_read_more(stream->parent, &data, &size);
+	size = I_MIN(size, IOSTREAM_LZ4_CHUNK_PREFIX_LEN - zstream->chunk_buf->used);
+	buffer_append(zstream->chunk_buf, data, size);
+	i_stream_skip(stream->parent, size);
+	if (ret < 0) {
+		stream->istream.stream_errno = stream->parent->stream_errno;
+		if (stream->istream.stream_errno == 0) {
+			stream->istream.eof = TRUE;
+			stream->cached_stream_size =
+				stream->istream.v_offset +
+				stream->pos - stream->skip;
+		}
+		return ret;
+	}
+	i_assert(ret != 0 || !stream->istream.blocking);
+	if (ret == 0)
+		return ret;
+	if (zstream->chunk_buf->used < IOSTREAM_LZ4_CHUNK_PREFIX_LEN)
+		return 0;
+	zstream->chunk_size = zstream->chunk_left =
+		be32_to_cpu_unaligned(zstream->chunk_buf->data);
+	if (zstream->chunk_size == 0 ||
+	    zstream->chunk_size > ISTREAM_LZ4_CHUNK_SIZE) {
+		lz4_read_error(zstream, t_strdup_printf(
+			"invalid lz4 chunk size: %u", zstream->chunk_size));
+		stream->istream.stream_errno = EINVAL;
+		return -1;
+	}
+	buffer_set_used_size(zstream->chunk_buf, 0);
+	return 1;
+}
+
 static ssize_t i_stream_lz4_read(struct istream_private *stream)
 {
 	struct lz4_istream *zstream = (struct lz4_istream *)stream;
@@ -105,38 +145,12 @@ static ssize_t i_stream_lz4_read(struct istream_private *stream)
 	}
 
 	if (zstream->chunk_left == 0) {
-		i_assert(zstream->chunk_buf->used <= IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
-		ret = i_stream_read_more(stream->parent, &data, &size);
-		if (size > IOSTREAM_LZ4_CHUNK_PREFIX_LEN - zstream->chunk_buf->used)
-			size = IOSTREAM_LZ4_CHUNK_PREFIX_LEN - zstream->chunk_buf->used;
-		buffer_append(zstream->chunk_buf, data, size);
-		i_stream_skip(stream->parent, size);
-		if (ret < 0) {
-			stream->istream.stream_errno =
-				stream->parent->stream_errno;
-			if (stream->istream.stream_errno == 0) {
-				stream->istream.eof = TRUE;
-				stream->cached_stream_size =
-					stream->istream.v_offset +
-					stream->pos - stream->skip;
-			}
-			return ret;
+		while ((ret = i_stream_lz4_read_chunk_header(zstream)) == 0) {
+			if (ret == 0 && !stream->istream.blocking)
+				return 0;
 		}
-		if (ret == 0 && !stream->istream.eof)
-			return 0;
-		if (zstream->chunk_buf->used < IOSTREAM_LZ4_CHUNK_PREFIX_LEN)
-			return 0;
-		zstream->chunk_size = zstream->chunk_left =
-			be32_to_cpu_unaligned(zstream->chunk_buf->data);
-		buffer_set_used_size(zstream->chunk_buf, 0);
-		if (zstream->chunk_size == 0 ||
-		    zstream->chunk_size > ISTREAM_LZ4_CHUNK_SIZE) {
-			lz4_read_error(zstream, t_strdup_printf(
-				"invalid lz4 chunk size: %u", zstream->chunk_size));
-			stream->istream.stream_errno = EINVAL;
-			return -1;
-		}
-		buffer_set_used_size(zstream->chunk_buf, 0);
+		if (ret < 0)
+			return ret;
 	}
 
 	/* read the whole compressed chunk into memory */
@@ -156,6 +170,7 @@ static ssize_t i_stream_lz4_read(struct istream_private *stream)
 		}
 		zstream->istream.istream.stream_errno =
 			zstream->istream.parent->stream_errno;
+		i_assert(ret != 0 || !stream->istream.blocking);
 		return ret;
 	}
 	/* if we already have max_buffer_size amount of data, fail here */