| 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 |
| Context | Check | Description |
|---|---|---|
| netdev/apply | fail | Patch does not apply to bpf |
| netdev/tree_selection | success | Clearly marked for bpf |
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 --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;
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(+)