[src/trunk]: src/sys/netinet Fix null deref, m could be NULL if M_PREPEND fails.

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

details:   https://anonhg.NetBSD.org/src/rev/64d9e934aee0
branches:  trunk
changeset: 829210:64d9e934aee0
user:      maxv <maxv%NetBSD.org@localhost>
date:      Mon Jan 22 09:51:06 2018 +0000

description:
Fix null deref, m could be NULL if M_PREPEND fails.

diffstat:

 sys/netinet/in_l2tp.c |  13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diffs (36 lines):

diff -r 757223fa3876 -r 64d9e934aee0 sys/netinet/in_l2tp.c
--- a/sys/netinet/in_l2tp.c     Mon Jan 22 09:45:32 2018 +0000
+++ b/sys/netinet/in_l2tp.c     Mon Jan 22 09:51:06 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: in_l2tp.c,v 1.9 2017/12/18 03:21:44 knakahara Exp $    */
+/*     $NetBSD: in_l2tp.c,v 1.10 2018/01/22 09:51:06 maxv Exp $        */
 
 /*
  * Copyright (c) 2017 Internet Initiative Japan Inc.
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: in_l2tp.c,v 1.9 2017/12/18 03:21:44 knakahara Exp $");
+__KERNEL_RCSID(0, "$NetBSD: in_l2tp.c,v 1.10 2018/01/22 09:51:06 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_l2tp.h"
@@ -196,11 +196,14 @@
 
        /* prepend new IP header */
        M_PREPEND(m, sizeof(struct ip), M_DONTWAIT);
+       if (m == NULL) {
+               error = ENOBUFS;
+               goto out;
+       }
        if (IP_HDR_ALIGNED_P(mtod(m, void *)) == 0) {
-               if (m)
-                       m = m_copyup(m, sizeof(struct ip), 0);
+               m = m_copyup(m, sizeof(struct ip), 0);
        } else {
-               if (m && m->m_len < sizeof(struct ip))
+               if (m->m_len < sizeof(struct ip))
                        m = m_pullup(m, sizeof(struct ip));
        }
        if (m == NULL) {