[PATCH] ipv6: prevent possible NULL dereference in ndisc_recv_na()

[Ma Ke]

In ndisc_recv_na(), __in6_dev_get() could return NULL, which is a NULL
pointer dereference. Add a check to prevent bailing out.

Fixes: 7a02bf892d8f ("ipv6: add option to drop unsolicited neighbor advertisements")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
 net/ipv6/ndisc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index d914b23256ce..f7cafff3f6a9 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1000,6 +1000,8 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb)
 	struct ndisc_options ndopts;
 	struct net_device *dev = skb->dev;
 	struct inet6_dev *idev = __in6_dev_get(dev);
+	if (!idev)
+		return SKP_DROP_REASON_NOT_SPECIFIED;
 	struct inet6_ifaddr *ifp;
 	struct neighbour *neigh;
 	SKB_DR(reason);
-- 
2.25.1