| Message ID | 9b79f43d2dfec8b2cb8e896b5591e7b1c3cc1f6c.1615288658.git.bnemeth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | net: prevent infinite loop caused by incorrect proto from virtio_net_hdr_set_proto | expand |
On Tue, Mar 9, 2021 at 6:32 AM Balazs Nemeth <bnemeth@redhat.com> wrote: > > 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> The compiler will convert that modulo into a cheap & (ETH_HLEN - 1) test for this constant.
On 3/9/21 4:31 AM, Balazs Nemeth wrote: > 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> > --- > net/mpls/mpls_gso.c | 3 +++ > 1 file changed, 3 insertions(+) > Reviewed-by: David Ahern <dsahern@kernel.org>
diff --git a/net/mpls/mpls_gso.c b/net/mpls/mpls_gso.c index b1690149b6fa..1482259de9b5 100644 --- 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;
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> --- net/mpls/mpls_gso.c | 3 +++ 1 file changed, 3 insertions(+)