From: Aki Tuomi <aki.tuomi@open-xchange.com>
Date: Fri, 12 Jun 2026 11:19:42 +0000 (+0000)
Subject: [PATCH 3/4] lib-compression: istream-zstd - Guard against no-progress loop in read
X-Git-Tag: archive/raspbian/1%2.4.1+dfsg1-6+rpi1+deb13u7^2~92
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=9ddba6188a1e2f5328b8caacb7328120a78b5e2b;p=dovecot.git

[PATCH 3/4] lib-compression: istream-zstd - Guard against no-progress loop in read

If ZSTD_decompressStream() returns with neither input consumed nor
output produced, the read loop would spin indefinitely. Add a check
after each call: if input.pos is unchanged and output.pos is zero,
treat it as a corrupt stream (EIO).

Gbp-Pq: Name 0003-lib-compression-istream-zstd-Guard-against-no-progre.patch
---

diff --git a/src/lib-compression/istream-zstd.c b/src/lib-compression/istream-zstd.c
index 9e059bc..b5505c8 100644
--- a/src/lib-compression/istream-zstd.c
+++ b/src/lib-compression/istream-zstd.c
@@ -175,12 +175,20 @@ static ssize_t i_stream_zstd_read(struct istream_private *stream)
 		zstream->output.pos = 0;
 		zstream->output.size = ZSTD_DStreamOutSize();
 
+		size_t old_input_pos = zstream->input.pos;
 		size_t zret = ZSTD_decompressStream(zstream->dstream, &zstream->output,
 						    &zstream->input);
 		if (ZSTD_isError(zret) != 0) {
 			i_stream_zstd_read_error(zstream, zret);
 			return -1;
 		}
+		if (zstream->input.pos == old_input_pos && zstream->output.pos == 0) {
+			io_stream_set_error(&zstream->istream.iostream,
+					    "zstd.read(%s): decompressor made no progress",
+					    i_stream_get_name(&zstream->istream.istream));
+			zstream->istream.istream.stream_errno = EIO;
+			return -1;
+		}
 		/* ZSTD magic number is 4 bytes, but it's only defined after v0.8 */
 		if (!zstream->hdr_read && zstream->input.size > 4)
 			zstream->hdr_read = TRUE;