net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0

A packet with skb_inner_network_header(skb) == skb_network_header(skb)
and ETH_P_MPLS_UC will prevent mpls_gso_segment from pulling any headers
from the packet. Subsequently, the call to skb_mac_gso_segment will
again call mpls_gso_segment with the same packet leading to an infinite
loop. In addition, ensure that the header length is a multiple of four,
which should hold irrespective of the number of stacked labels.

Signed-off-by: Balazs Nemeth <bnemeth@redhat.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c
index b169014..1482259 100644 (file)
--- a/net/mpls/mpls_gso.c
+++ b/net/mpls/mpls_gso.c
@@ -14,6 +14,7 @@
 #include <linux/netdev_features.h>
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
+#include <net/mpls.h>
 
 static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
                                       netdev_features_t features)
@@ -27,6 +28,8 @@ static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
 
        skb_reset_network_header(skb);
        mpls_hlen = skb_inner_network_header(skb) - skb_network_header(skb);
+       if (unlikely(!mpls_hlen || mpls_hlen % MPLS_HLEN))
+               goto out;
        if (unlikely(!pskb_may_pull(skb, mpls_hlen)))
                goto out;