From 129f9fc0c8e9787dee3db5a6f65c3370ed148f7e Mon Sep 17 00:00:00 2001
From: Zettroke <zettroke@protonmail.com>
Date: Wed, 4 Dec 2024 13:18:14 +0300
Subject: [PATCH] codec: fix incorrect handling of invalid utf-8 in
 `LinesCodec::decode_eof` (#7011)

---
 tokio-util/src/codec/lines_codec.rs |  2 +-
 tokio-util/tests/codecs.rs          | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tokio-util/src/codec/lines_codec.rs b/tokio-util/src/codec/lines_codec.rs
index 47f68d88fda..cc1ac4ebdad 100644
--- a/tokio-util/src/codec/lines_codec.rs
+++ b/tokio-util/src/codec/lines_codec.rs
@@ -169,6 +169,7 @@ impl Decoder for LinesCodec {
         Ok(match self.decode(buf)? {
             Some(frame) => Some(frame),
             None => {
+                self.next_index = 0;
                 // No terminating newline - return remaining data, if any
                 if buf.is_empty() || buf == &b"\r"[..] {
                     None
@@ -176,7 +177,6 @@ impl Decoder for LinesCodec {
                     let line = buf.split_to(buf.len());
                     let line = without_carriage_return(&line);
                     let line = utf8(line)?;
-                    self.next_index = 0;
                     Some(line.to_string())
                 }
             }
diff --git a/tokio-util/tests/codecs.rs b/tokio-util/tests/codecs.rs
index 1cfd9208e86..57743be7155 100644
--- a/tokio-util/tests/codecs.rs
+++ b/tokio-util/tests/codecs.rs
@@ -62,6 +62,19 @@ fn lines_decoder() {
     assert_eq!(None, codec.decode_eof(buf).unwrap());
 }
 
+#[test]
+fn lines_decoder_invalid_utf8() {
+    let mut codec = LinesCodec::new();
+    let buf = &mut BytesMut::new();
+    buf.reserve(200);
+    buf.put_slice(b"line 1\xc3\x28");
+    assert_eq!(None, codec.decode(buf).unwrap());
+    assert!(codec.decode_eof(buf).is_err());
+    assert_eq!(None, codec.decode_eof(buf).unwrap());
+    buf.put_slice(b"line 22222222222222\n");
+    assert_eq!("line 22222222222222", codec.decode(buf).unwrap().unwrap());
+}
+
 #[test]
 fn lines_decoder_max_length() {
     const MAX_LENGTH: usize = 6;