[sudo-workers] visudo edit wrong file

[Todd C. Miller]

Confirmed.  This bug was introduced in 1.8.14 with the refactoring
of the editing code.  The patch below will work around the issue.
For sudo 1.8.15 I'm going to rearrange things a bit to make this
unnecessary.

 - todd

diff -r 2b3efe0a91f2 plugins/sudoers/visudo.c
--- a/plugins/sudoers/visudo.c	Thu Sep 10 16:44:57 2015 -0600
+++ b/plugins/sudoers/visudo.c	Tue Sep 15 09:26:35 2015 -0600
@@ -465,14 +465,15 @@
 	lineno = -1;
 
     /*
-     * We pre-allocated 2 extra spaces for "+n filename" in argv.
+     * The last 3 slots in the editor argv are: "-- +1 sudoers"
      * Replace those placeholders with the real values.
      */
-    ac = editor_argc - 2;
+    ac = editor_argc - 3;
     if (lineno > 0) {
 	(void)snprintf(linestr, sizeof(linestr), "+%d", lineno);
 	editor_argv[ac++] = linestr;
     }
+    editor_argv[ac++] = "--";
     editor_argv[ac++] = sp->tpath;
     editor_argv[ac++] = NULL;