diff mbox series

[bpf,v4,1/2] bpf: Set mac_len in bpf_skb_change_head

Message ID 20210519154743.2554771-2-joamaki@gmail.com (mailing list archive)
State Accepted
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 19, 2021, 3:47 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(+)

Comments

Daniel Borkmann May 20, 2021, 10:07 p.m. UTC | #1
On 5/19/21 5:47 PM, Jussi Maki wrote:
> 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>

Took this one in, the selftest needs a rebase since it doesn't apply to
bpf. Pls fix and resubmit 2/2, thanks.
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;