[PATCH 4.14 04/34] ipv4/route: fail early when inet dev is missing

Greg Kroah-Hartman
2019-03-18T09:35:51Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit 22c74764aa2943ecdf9f07c900d8a9c8ba6c9265 ]

If a non local multicast packet reaches ip_route_input_rcu() while
the ingress device IPv4 private data (in_dev) is NULL, we end up
doing a NULL pointer dereference in IN_DEV_MFORWARD().

Since the later call to ip_route_input_mc() is going to fail if
!in_dev, we can fail early in such scenario and avoid the dangerous
code path.

v1 -> v2:
- clarified the commit message, no code changes

Reported-by: Tianhao Zhao <tizhao@redhat.com>
Fixes: e58e41596811 ("net: Enable support for VRF with ipv4 multicast")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/route.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2123,12 +2123,13 @@ int ip_route_input_rcu(struct sk_buff *s
int our = 0;
int err = -EINVAL;

- if (in_dev)
- our = ip_check_mc_rcu(in_dev, daddr, saddr,
- ip_hdr(skb)->protocol);
+ if (!in_dev)
+ return err;
+ our = ip_check_mc_rcu(in_dev, daddr, saddr,
+ ip_hdr(skb)->protocol);

/* check l3 master if no match yet */
- if ((!in_dev || !our) && netif_is_l3_slave(dev)) {
+ if (!our && netif_is_l3_slave(dev)) {
struct in_device *l3_in_dev;

l3_in_dev = __in_dev_get_rcu(skb->dev);