Subject: Prevent segfault for formUpdateBuffer
Author: Tatsuya Kinoshita <tats@debian.org>
Bug-Debian: https://github.com/tats/w3m/issues/9 [CVE-2016-9423]
Bug-Debian: https://github.com/tats/w3m/issues/10 [CVE-2016-9431]
Origin: https://anonscm.debian.org/cgit/collab-maint/w3m.git/commit/?id=9f0bdcfdf061db3520bd1f112bdc5e83acdec4be

diff --git a/form.c b/form.c
index 62b568e..87a5d49 100644
--- a/form.c
+++ b/form.c
@@ -477,6 +477,8 @@ formUpdateBuffer(Anchor *a, Buffer *buf, FormItemList *form)
 		spos = a->start.pos;
 		epos = a->end.pos;
 	    }
+	    if (a->start.line != a->end.line || spos > epos)
+		epos = spos;
 	    pos = form_update_line(l, &p, spos, epos, COLPOS(l, epos) - col,
 				   rows > 1,
 				   form->type == FORM_INPUT_PASSWORD);