listener: fix buffer overflow reading external file.

When an external file is edited, and is longer than the
listener's buffer allows, the buffer overflows, trashing the
other fields in the linenoise structure, and memory beyond.

* parser.c (lino_gets): Decrement nchar in the loop.
Also, eliminate useless return case.

1 files changed, 1 insertions, 6 deletions

diff --git a/parser.c b/parser.c
index d0c4b7a9..0f5d5c99 100644
--- a/parser.c
+++ b/parser.c
@@ -1496,18 +1496,13 @@ static wchar_t *lino_gets(mem_t *stream_in, wchar_t *buf, size_t nchar)
   if (nchar == 0)
     return buf;
 
-  while (nchar > 1) {
+  while (nchar-- > 1) {
     val ch = get_char(stream);
     if (!ch)
       break;
     *ptr++ = c_num(ch);
   }
 
-  if (ptr == buf) {
-    *ptr++ = 0;
-    return 0;
-  }
-
   *ptr++ = 0;
   return buf;
 }