Cong Wang wrote:
> From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
>
> skb_network_offset() and skb_transport_offset() can be negative when
> they are called after we pull the transport header, for example, when
> we use eBPF sockmap at the point of ->sk_data_ready().
>
> __bpf_skb_min_len() uses an unsigned int to get these offsets, this
> leads to a very large number which then causes bpf_skb_change_tail()
> failed unexpectedly.
>
> Fix this by using a signed int to get these offsets and ensure the
> minimum is at least zero.
>
> Fixes: 5293efe62df8 ("bpf: add bpf_skb_change_tail helper")
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> ---
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
