From 786a9368be8cf862f1c290edb17c1a7ae363c059 Mon Sep 17 00:00:00 2001 From: Lorenzo Bianconi Date: Fri, 31 Jul 2020 20:12:05 +0200 Subject: net: gre: recompute gre csum for sctp over gre tunnels [ Upstream commit 622e32b7d4a6492cf5c1f759ef833f817418f7b3 ] The GRE tunnel can be used to transport traffic that does not rely on a Internet checksum (e.g. SCTP). The issue can be triggered creating a GRE or GRETAP tunnel and transmitting SCTP traffic ontop of it where CRC offload has been disabled. In order to fix the issue we need to recompute the GRE csum in gre_gso_segment() not relying on the inner checksum. The issue is still present when we have the CRC offload enabled. In this case we need to disable the CRC offload if we require GRE checksum since otherwise skb_checksum() will report a wrong value. Fixes: 90017accff61 ("sctp: Add GSO support") Signed-off-by: Lorenzo Bianconi Reviewed-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/gre_offload.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c index 4de7e962d3da..c840141876bc 100644 --- a/net/ipv4/gre_offload.c +++ b/net/ipv4/gre_offload.c @@ -15,12 +15,12 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, netdev_features_t features) { int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb); + bool need_csum, need_recompute_csum, gso_partial; struct sk_buff *segs = ERR_PTR(-EINVAL); u16 mac_offset = skb->mac_header; __be16 protocol = skb->protocol; u16 mac_len = skb->mac_len; int gre_offset, outer_hlen; - bool need_csum, gso_partial; if (!skb->encapsulation) goto out; @@ -41,6 +41,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, skb->protocol = skb->inner_protocol; need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM); + need_recompute_csum = skb->csum_not_inet; skb->encap_hdr_csum = need_csum; features &= skb->dev->hw_enc_features; @@ -98,7 +99,15 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, } *(pcsum + 1) = 0; - *pcsum = gso_make_checksum(skb, 0); + if (need_recompute_csum && !skb_is_gso(skb)) { + __wsum csum; + + csum = skb_checksum(skb, gre_offset, + skb->len - gre_offset, 0); + *pcsum = csum_fold(csum); + } else { + *pcsum = gso_make_checksum(skb, 0); + } } while ((skb = skb->next)); out: return segs; -- cgit v1.2.3