lib: istream-concat - Fix potential hang when reaching max buffer size

diff --git a/src/lib/istream-concat.c b/src/lib/istream-concat.c
index 253edd6f6027eb999fe325238056b92cf63de006..a4860549ff77bc8b56088a7000c67778a87a0177 100644 (file)
--- a/src/lib/istream-concat.c
+++ b/src/lib/istream-concat.c
@@ -227,6 +227,13 @@ static ssize_t i_stream_concat_read(struct istream_private *stream)
                        return -2;
                }
                stream->buffer = stream->w_buffer;
+               if (size < new_bytes_count) {
+                       /* Everything couldn't be added to the concat-istream's
+                          buffer. However, parent istream still contains data
+                          in its buffer and it might not be receiving more.
+                          Make sure the istream won't hang. */
+                       i_stream_set_input_pending(&stream->istream, TRUE);
+               }
 
                /* we'll copy all the new input to w_buffer. if we skip over
                   prev_stream_left bytes, the next read will switch to