lib/53981: libedit: history_list should null-terminate

[jperkins+netbsd%google.com@localhost]

>Number:         53981
>Category:       lib
>Synopsis:       libedit: history_list should null-terminate
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 14 19:10:00 +0000 2019
>Originator:     Jonathan Perkins
>Release:        Sources as of 2019/02/14
>Organization:
Google
>Environment:
>Description:
Readline documents that history_list is null-terminated.  At present, history_list in libedit doesn't null-terminate; it'd be helpful to add the null terminator for compatibility.

This can be addressed with a small change to _history_listp, as indicated in the proposed patch.

(this is one of a few issues I've run into trying to reach readline compatibility, I'll submit more patches if this is helpful)
>How-To-Repeat:
On calling history_list(), iterator through the HIST_ENTRY**, looking for a null terminator.
>Fix:
--- old/src/readline.c
+++ new/src/readline.c
@@ -1600,7 +1600,7 @@ history_list(void)
 		return NULL;
 
 	if ((nlp = el_realloc(_history_listp,
-	    (size_t)history_length * sizeof(*nlp))) == NULL)
+	    ((size_t)history_length + 1) * sizeof(*nlp))) == NULL)
 		return NULL;
 	_history_listp = nlp;
 
@@ -1617,6 +1617,7 @@ history_list(void)
 		if (i++ == history_length)
 			abort();
 	} while (history(h, &ev, H_PREV) == 0);
+	_history_listp[i] = NULL;
 	return _history_listp;
 }