Bug#20318154 : NEGATIVE ARRAY INDEX WRITE V2

Description:- There is a possibility of negative array index
write associated with the function "terminal_writec()". This
is due to the assumption that there is a possibility of
getting -1 return value from the function call
"ct_visual_char()".

Analysis:- The function "terminal_writec()" is called only
from "em_delete_or_list()" and "vi_list_or_eof()" and both
these functions deal with the "^D" (ctrl+D) signal. So the
"size_t len" and "Char c" passed to "ct_visual_char()" (when
called from "terminal_writec()") is always 8 (macro
VISUAL_WIDTH_MAX is passed whose value is 8) and 4 (ASCII
value for "^D"/"ctrl+D") respectively.
Since the value of "c" is 4, "ct_chr_class()" returns -1
(macro CHTYPE_ASCIICTL is associated with -1 value). And
since value of "len" is 8, "ct_visual_char()" will always
return 2 when it is called from "terminal_writec()".
So there is no possible case so that we encounter a negative
array index write in "terminal_writec()". But since there is
a rare posibility of using "terminal_writec()" in future
enhancements, it is good handle the error case as well.

Fix:- A condition is added in "terminal_writec()" to check
whether "ct_visual_char()" is returning -1 or not. If the
return value is -1, then value 0 is returned to its calling
function "em_delete_or_list()" or "vi_list_or_eof()", which
in turn will return CC_ERROR.

NOTE:- No testcase is added since currently there is no
possible scenario to encounter this error case.

cmd-line-utils/libedit/el_terminal.h

 /*	$NetBSD: terminal.h,v 1.3 2011/07/29 23:44:45 christos Exp $	*/
 
 /*-
- * Copyright (c) 1992, 1993
+ * Copyright (c) 1992, 2015
  *	The Regents of the University of California.  All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
@@ -103,7 +103,7 @@ protected int	terminal_settc(EditLine *, int, const Char **);
 protected int	terminal_gettc(EditLine *, int, char **);
 protected int	terminal_telltc(EditLine *, int, const Char **);
 protected int	terminal_echotc(EditLine *, int, const Char **);
-protected void	terminal_writec(EditLine *, Int);
+protected int	terminal_writec(EditLine *, Int);
 protected int	terminal__putc(EditLine *, Int);
 protected void	terminal__flush(EditLine *);
 

cmd-line-utils/libedit/emacs.c

 /*	$NetBSD: emacs.c,v 1.25 2011/07/29 15:16:33 christos Exp $	*/
 
 /*-
- * Copyright (c) 1992, 1993
+ * Copyright (c) 1992, 2015
  *	The Regents of the University of California.  All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
@@ -58,8 +58,10 @@ em_delete_or_list(EditLine *el, Int c)
 					/* if I'm at the end */
 		if (el->el_line.cursor == el->el_line.buffer) {
 					/* and the beginning */
-			terminal_writec(el, c);	/* then do an EOF */
-			return CC_EOF;
+			if(!(terminal_writec(el, c)))	/* then do an EOF */
+				return CC_EOF;
+			else
+				return CC_ERROR;
 		} else {
 			/*
 			 * Here we could list completions, but it is an

cmd-line-utils/libedit/terminal.c

 /*	$NetBSD: terminal.c,v 1.10 2011/10/04 15:27:04 christos Exp $	*/
 
 /*-
- * Copyright (c) 1992, 1993
+ * Copyright (c) 1992, 2015
  *	The Regents of the University of California.  All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
@@ -1271,14 +1271,19 @@ terminal__flush(EditLine *el)
 /* terminal_writec():
  *	Write the given character out, in a human readable form
  */
-protected void
+protected int
 terminal_writec(EditLine *el, Int c)
 {
 	Char visbuf[VISUAL_WIDTH_MAX +1];
 	ssize_t vcnt = ct_visual_char(visbuf, VISUAL_WIDTH_MAX, c);
-	visbuf[vcnt] = '\0';
-	terminal_overwrite(el, visbuf, (size_t)vcnt);
-	terminal__flush(el);
+	if(vcnt == -1)
+		return 1;   /* Error due to insufficient space */
+	else {
+		visbuf[vcnt] = '\0';
+		terminal_overwrite(el, visbuf, (size_t)vcnt);
+		terminal__flush(el);
+		return 0;
+	}
 }
 
 

cmd-line-utils/libedit/vi.c

 /*	$NetBSD: vi.c,v 1.41 2011/10/04 15:27:04 christos Exp $	*/
 
 /*-
- * Copyright (c) 1992, 1993
+ * Copyright (c) 1992, 2015
  *	The Regents of the University of California.  All rights reserved.
  *
  * This code is derived from software contributed to Berkeley by
@@ -607,8 +607,10 @@ vi_list_or_eof(EditLine *el, Int c)
 
 	if (el->el_line.cursor == el->el_line.lastchar) {
 		if (el->el_line.cursor == el->el_line.buffer) {
-			terminal_writec(el, c);	/* then do a EOF */
-			return CC_EOF;
+			if(!(terminal_writec(el, c)))	/* then do a EOF */
+				return CC_EOF;
+			else
+				return CC_ERROR;
 		} else {
 			/*
 			 * Here we could list completions, but it is an