[src/trunk]: src/sys/arch/x86/x86 Add a NULL check on the structure pointer, ...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/c1aa1ee49ad5
branches:  trunk
changeset: 1004823:c1aa1ee49ad5
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Nov 16 10:19:29 2019 +0000

description:
Add a NULL check on the structure pointer, not to retrieve its first field
if it is NULL. The previous code was not buggy strictly speaking. This
change probably doesn't change anything, except removing assumptions in the
compiler optimization passes, which too probably doesn't change anything in
this case.

Reported-by: syzbot+110b29c1973f38a38026%syzkaller.appspotmail.com@localhost

diffstat:

 sys/arch/x86/x86/pmap.c |  6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diffs (27 lines):

diff -r 62b80c530b6e -r c1aa1ee49ad5 sys/arch/x86/x86/pmap.c
--- a/sys/arch/x86/x86/pmap.c   Sat Nov 16 10:15:10 2019 +0000
+++ b/sys/arch/x86/x86/pmap.c   Sat Nov 16 10:19:29 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.340 2019/11/14 17:09:23 maxv Exp $  */
+/*     $NetBSD: pmap.c,v 1.341 2019/11/16 10:19:29 maxv Exp $  */
 
 /*
  * Copyright (c) 2008, 2010, 2016, 2017 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.340 2019/11/14 17:09:23 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.341 2019/11/16 10:19:29 maxv Exp $");
 
 #include "opt_user_ldt.h"
 #include "opt_lockdebug.h"
@@ -541,6 +541,8 @@
 pve_to_pvpte(struct pv_entry *pve)
 {
 
+       if (pve == NULL)
+               return NULL;
        KASSERT((void *)&pve->pve_pte == (void *)pve);
        return &pve->pve_pte;
 }