linux-kernel - Re: netlink: NULL timer crash

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Date:   Thu, 23 Mar 2017 09:00:58 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        David Miller <davem@...emloft.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Alexei Starovoitov <ast@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: netlink: NULL timer crash

On Thu, 2017-03-23 at 07:53 -0700, Eric Dumazet wrote:

> Nice !
> 
> Looks like neigh->ops->solicit is NULL

Apparently we allow admins to do really stupid things with neighbours
on tunnels.

Following patch should avoid the crash.

Anyone has better ideas ?


 net/ipv4/arp.c   |    5 +++++
 net/ipv6/ndisc.c |    4 ++++
 2 files changed, 9 insertions(+)

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 51b27ae09fbd725bcd8030982e5850215ac4ce5c..963191b12e28041bf5df6f37f222a7155f83a414 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -146,8 +146,13 @@ static const struct neigh_ops arp_hh_ops = {
 	.connected_output =	neigh_resolve_output,
 };
 
+static void arp_no_solicit(struct neighbour *neigh, struct sk_buff *skb)
+{
+}
+
 static const struct neigh_ops arp_direct_ops = {
 	.family =		AF_INET,
+	.solicit =		arp_no_solicit,
 	.output =		neigh_direct_output,
 	.connected_output =	neigh_direct_output,
 };
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 7ebac630d3c603186be2fc0dcbaac7d7e74bfde6..86f290b749d5ca0db4310b17ebeff35d847540c7 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -99,9 +99,13 @@ static const struct neigh_ops ndisc_hh_ops = {
 	.connected_output =	neigh_resolve_output,
 };
 
+static void ndisc_no_solicit(struct neighbour *neigh, struct sk_buff *skb)
+{
+}
 
 static const struct neigh_ops ndisc_direct_ops = {
 	.family =		AF_INET6,
+	.solicit =		ndisc_no_solicit,
 	.output =		neigh_direct_output,
 	.connected_output =	neigh_direct_output,
 };