From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Tue, 3 Jun 2025 15:11:09 +0000 (+0300)
Subject: lib-compression: Fix potential hangs writing to non-blocking ostreams
X-Git-Tag: 2.4.2~670
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8f04ede4b55bc63cc48ae41a544f836ed2d35720;p=thirdparty%2Fdovecot%2Fcore.git

lib-compression: Fix potential hangs writing to non-blocking ostreams

This especially fixes hangs with IMAP COMPRESS handling in proxies.
---

diff --git a/src/lib-compression/ostream-bzlib.c b/src/lib-compression/ostream-bzlib.c
index 839fd22138..c7e228b05a 100644
--- a/src/lib-compression/ostream-bzlib.c
+++ b/src/lib-compression/ostream-bzlib.c
@@ -94,6 +94,11 @@ static int o_stream_zlib_send_outbuf(struct bzlib_ostream *zstream)
 	}
 	if ((size_t)ret != size) {
 		zstream->outbuf_offset += ret;
+		/* We couldn't send everything to parent stream, but we
+		   accepted all the input already. Set the ostream's flush
+		   pending so when there's more space in the parent stream
+		   we'll continue sending the rest of the data. */
+		o_stream_set_flush_pending(&zstream->ostream.ostream, TRUE);
 		return 0;
 	}
 	zstream->outbuf_offset = 0;
@@ -301,6 +306,7 @@ static struct ostream *o_stream_create_bz2(struct ostream *output, int level)
 
 	zstream->zs.next_out = zstream->outbuf;
 	zstream->zs.avail_out = sizeof(zstream->outbuf);
+	o_stream_init_buffering_flush(&zstream->ostream, output);
 	return o_stream_create(&zstream->ostream, output,
 			       o_stream_get_fd(output));
 }
diff --git a/src/lib-compression/ostream-lz4.c b/src/lib-compression/ostream-lz4.c
index 65961603ae..0707e12d43 100644
--- a/src/lib-compression/ostream-lz4.c
+++ b/src/lib-compression/ostream-lz4.c
@@ -50,6 +50,11 @@ static int o_stream_lz4_send_outbuf(struct lz4_ostream *zstream)
 	}
 	if ((size_t)ret != size) {
 		zstream->outbuf_offset += ret;
+		/* We couldn't send everything to parent stream, but we
+		   accepted all the input already. Set the ostream's flush
+		   pending so when there's more space in the parent stream
+		   we'll continue sending the rest of the data. */
+		o_stream_set_flush_pending(&zstream->ostream.ostream, TRUE);
 		return 0;
 	}
 	zstream->outbuf_offset = 0;
@@ -226,6 +231,7 @@ o_stream_create_lz4_auto(struct ostream *output,
 	hdr->max_uncompressed_chunk_size[3] =
 		(OSTREAM_LZ4_CHUNK_SIZE & 0x000000ff);
 	zstream->outbuf_used = sizeof(*hdr);
+	o_stream_init_buffering_flush(&zstream->ostream, output);
 	return o_stream_create(&zstream->ostream, output,
 			       o_stream_get_fd(output));
 }
diff --git a/src/lib-compression/ostream-zlib.c b/src/lib-compression/ostream-zlib.c
index 1367713e68..5cc2215737 100644
--- a/src/lib-compression/ostream-zlib.c
+++ b/src/lib-compression/ostream-zlib.c
@@ -109,7 +109,11 @@ static int o_stream_zlib_send_gz_header(struct zlib_ostream *zstream)
 	}
 	i_assert((size_t)ret <= zstream->header_bytes_left);
 	zstream->header_bytes_left -= ret;
-	return zstream->header_bytes_left == 0 ? 1 : 0;
+	if (zstream->header_bytes_left != 0) {
+		o_stream_set_flush_pending(&zstream->ostream.ostream, TRUE);
+		return 0;
+	}
+	return 1;
 }
 
 static int o_stream_zlib_lsb_uint32(struct ostream *output, uint32_t num)
@@ -159,6 +163,11 @@ static int o_stream_zlib_send_outbuf(struct zlib_ostream *zstream)
 	}
 	if ((size_t)ret != size) {
 		zstream->outbuf_offset += ret;
+		/* We couldn't send everything to parent stream, but we
+		   accepted all the input already. Set the ostream's flush
+		   pending so when there's more space in the parent stream
+		   we'll continue sending the rest of the data. */
+		o_stream_set_flush_pending(&zstream->ostream.ostream, TRUE);
 		return 0;
 	}
 	zstream->outbuf_offset = 0;
@@ -414,6 +423,7 @@ o_stream_create_zlib(struct ostream *output, int level, bool gz)
 
 	zstream->zs.next_out = zstream->outbuf;
 	zstream->zs.avail_out = sizeof(zstream->outbuf);
+	o_stream_init_buffering_flush(&zstream->ostream, output);
 	return o_stream_create(&zstream->ostream, output,
 			       o_stream_get_fd(output));
 }
diff --git a/src/lib-compression/ostream-zstd.c b/src/lib-compression/ostream-zstd.c
index 786765f137..b307fefd60 100644
--- a/src/lib-compression/ostream-zstd.c
+++ b/src/lib-compression/ostream-zstd.c
@@ -115,8 +115,14 @@ static ssize_t o_stream_zstd_send_outbuf(struct zstd_ostream *zstream)
 		memmove(zstream->outbuf, zstream->outbuf+ret, zstream->output.pos-ret);
 		zstream->output.pos -= ret;
 	}
-	if (zstream->output.pos > 0)
+	if (zstream->output.pos > 0) {
+		/* We couldn't send everything to parent stream, but we
+		   accepted all the input already. Set the ostream's flush
+		   pending so when there's more space in the parent stream
+		   we'll continue sending the rest of the data. */
+		o_stream_set_flush_pending(&zstream->ostream.ostream, TRUE);
 		return 0;
+	}
 	return 1;
 }
 
@@ -263,6 +269,7 @@ o_stream_create_zstd(struct ostream *output, int level)
 		zstream->output.dst = zstream->outbuf;
 		zstream->output.size = ZSTD_CStreamOutSize();
 	}
+	o_stream_init_buffering_flush(&zstream->ostream, output);
 	return o_stream_create(&zstream->ostream, output,
 			       o_stream_get_fd(output));
 }