From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Tue, 8 Sep 2020 18:19:21 +0000 (+0300)
Subject: lib-compression: ostream-zstd - Fix assert-crash with large input
X-Git-Tag: 2.3.13~232
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a96e742047635ecb8df67c9dbb36b05e0b8fa8e6;p=thirdparty%2Fdovecot%2Fcore.git

lib-compression: ostream-zstd - Fix assert-crash with large input

If the input was large enough, the ostream write could have returned
partially written output. Since this ostream-zstd was only used for
blocking ostreams, this would always result in an assert-crash. Fix is
to keep flushing the output to parent if the output buffer becomes full.

Fixes:
Panic: file ostream.c: line 287 (o_stream_sendv_int): assertion failed: (!stream->blocking)
---

diff --git a/src/lib-compression/ostream-zstd.c b/src/lib-compression/ostream-zstd.c
index bc3c5e2c43..cbf660395a 100644
--- a/src/lib-compression/ostream-zstd.c
+++ b/src/lib-compression/ostream-zstd.c
@@ -82,24 +82,37 @@ o_stream_zstd_sendv(struct ostream_private *stream,
 
 	for (unsigned int i = 0; i < iov_count; i++) {
 		/* does it actually fit there */
-		if (zstream->output.pos + iov[i].iov_len >= zstream->output.size)
-			break;
 		ZSTD_inBuffer input = {
 			.src = iov[i].iov_base,
 			.pos = 0,
 			.size = iov[i].iov_len
 		};
-		ret = ZSTD_compressStream(zstream->cstream, &zstream->output,
-					  &input);
-		if (ZSTD_isError(ret) != 0) {
-			o_stream_zstd_write_error(zstream, ret);
-			return -1;
+		bool flush_attempted = FALSE;
+		for (;;) {
+			size_t prev_pos = input.pos;
+			ret = ZSTD_compressStream(zstream->cstream, &zstream->output,
+						  &input);
+			if (ZSTD_isError(ret) != 0) {
+				o_stream_zstd_write_error(zstream, ret);
+				return -1;
+			}
+			size_t new_input_size = input.pos - prev_pos;
+			if (new_input_size == 0 && flush_attempted) {
+				/* non-blocking output buffer full */
+				return total;
+			}
+			stream->ostream.offset += new_input_size;
+			total += new_input_size;
+			if (input.pos == input.size)
+				break;
+			/* output buffer full. try to flush it. */
+			if (o_stream_zstd_send_outbuf(zstream) < 0)
+				return -1;
+			flush_attempted = TRUE;
 		}
-		total += input.pos;
 	}
 	if (o_stream_zstd_send_outbuf(zstream) < 0)
 		return -1;
-	stream->ostream.offset += total;
 	return total;
 }