Re: [PATCH net v3 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
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 > --- > net/mpls/mpls_gso.c | 3 +++ > 1 file changed, 3 insertions(+) > Reviewed-by: David Ahern
Re: [PATCH net v3 2/2] net: avoid infinite loop in mpls_gso_segment when mpls_hlen == 0
On Tue, Mar 9, 2021 at 6:32 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 Acked-by: Willem de Bruijn The compiler will convert that modulo into a cheap & (ETH_HLEN - 1) test for this constant.
[PATCH net v3 2/2] 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 --- net/mpls/mpls_gso.c | 3 +++ 1 file changed, 3 insertions(+) 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 #include #include +#include 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; -- 2.29.2
