Re: Crash in mandoc HEAD

[Ingo Schwarze <schwarze@usta.de>]

Hi Kristaps,

Kristaps Dzonsons wrote on Fri, Aug 15, 2014 at 03:53:49PM +0200:

> I managed to crash mandoc(1) today while formatting a manual.
> Narrowed down:
> 
>      1	.Dd $Mdocdate$
>      2	.Dt FOO 1
>      3	.Os
>      4	.Sh NAME
>      5	.Nm foo
>      6	.Nd bar
>      7	.Sh DESCRIPTION
>      8	The
>      9	.Bl -hang
>     10	.It Nm Fo o
>     11	xyzzy
>     12	.El
> 
> In short, the "Fo" is continuing a node subtree perpetually and the
> HEAD for the "It" on line 10 just keeps going.  There's a check for
> "n->next->child" which thus crashes because "n->next" is NULL.
> 
> The fix is very simple and enclosed.

That's nearly right, but insufficient, the same pointer is
accessed a second time a few lines below, so it still crashes.

Please commit ASAP in the following form, I'll take care of the
merging.

Thanks,
  Ingo


Index: mdoc_term.c
===================================================================
RCS file: /cvs/src/usr.bin/mandoc/mdoc_term.c,v
retrieving revision 1.177
diff -u -p -r1.177 mdoc_term.c
--- mdoc_term.c	8 Aug 2014 16:17:09 -0000	1.177
+++ mdoc_term.c	17 Aug 2014 04:08:09 -0000
@@ -804,7 +804,7 @@ termp_it_pre(DECL_ARGS)
 		 * the "overstep" effect in term_flushln() and treat
 		 * this as a `-ohang' list instead.
 		 */
-		if (n->next->child &&
+		if (NULL != n->next && NULL != n->next->child &&
 		    (MDOC_Bl == n->next->child->tok ||
 		     MDOC_Bd == n->next->child->tok))
 			break;
@@ -860,7 +860,8 @@ termp_it_pre(DECL_ARGS)
 		 * don't want to recalculate rmargin and offsets when
 		 * using `Bd' or `Bl' within `-hang' overstep lists.
 		 */
-		if (MDOC_HEAD == n->type && n->next->child &&
+		if (MDOC_HEAD == n->type &&
+		    NULL != n->next && NULL != n->next->child &&
 		    (MDOC_Bl == n->next->child->tok ||
 		     MDOC_Bd == n->next->child->tok))
 			break;
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