diff mbox series

[bpf,v3,1/2] bpf: Set mac_len in bpf_skb_change_head

Message ID 20210518142356.1852779-2-joamaki@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Fix l3 to l2 use of bpf_skb_change_head | expand

Checks

Context Check Description
netdev/apply fail Patch does not apply to bpf
netdev/tree_selection success Clearly marked for bpf

Commit Message

Jussi Maki May 18, 2021, 2:23 p.m. UTC 
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 <joamaki@gmail.com>
---
 net/core/filter.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/net/core/filter.c b/net/core/filter.c
index cae56d08a670..65ab4e21c087 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;