From dc1dc86d4153cbbbed2878c9c2ef55a7d0f9581f Mon Sep 17 00:00:00 2001 From: Jussi Maki Date: Wed, 19 May 2021 15:47:42 +0000 Subject: [PATCH] bpf: Set mac_len in bpf_skb_change_head [ Upstream commit 84316ca4e100d8cbfccd9f774e23817cb2059868 ] The skb_change_head() helper did not set "skb->mac_len", which is problematic when it's used in combination with skb_redirect_peer(). Without it, redirecting a packet from a L3 device such as wireguard to the veth peer device will cause skb->data to point to the middle of the IP header on entry to tcp_v4_rcv() since the L2 header is not pulled correctly due to mac_len=0. Fixes: 3a0af8fd61f9 ("bpf: BPF for lightweight tunnel infrastructure") Signed-off-by: Jussi Maki Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210519154743.2554771-2-joamaki@gmail.com Signed-off-by: Sasha Levin --- net/core/filter.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/core/filter.c b/net/core/filter.c index e4c48941d83e..98b8057e2382 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2438,6 +2438,7 @@ BPF_CALL_3(bpf_skb_change_head, struct sk_buff *, skb, u32, head_room, __skb_push(skb, head_room); memset(skb->data, 0, head_room); skb_reset_mac_header(skb); + skb_reset_mac_len(skb); } bpf_compute_data_end(skb); -- 2.20.1