From: Jussi Maki Date: Wed, 19 May 2021 15:47:42 +0000 (+0000) Subject: bpf: Set mac_len in bpf_skb_change_head X-Git-Tag: v5.13-rc4~29^2~1^2~7 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=84316ca4e100d8cbfccd9f774e23817cb2059868;p=thirdparty%2Fkernel%2Flinux.git bpf: Set mac_len in bpf_skb_change_head 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 --- diff --git a/net/core/filter.c b/net/core/filter.c index cae56d08a6707..65ab4e21c087f 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3784,6 +3784,7 @@ static inline int __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); } return ret;