Re: [PATCH net] net: dsa: ksz: don't pad a cloned sk_buff

[Andrew Lunn]

On Fri, Oct 16, 2020 at 09:35:27AM +0200, Christian Eggers wrote:
> If the supplied sk_buff is cloned (e.g. in dsa_skb_tx_timestamp()),
> __skb_put_padto() will allocate a new sk_buff with size = skb->len +
> padlen. So the condition just tested for (skb_tailroom(skb) >= padlen +
> len) is not fulfilled anymore. Although the real size will usually be
> larger than skb->len + padlen (due to alignment), there is no guarantee
> that the required memory for the tail tag will be available
> 
> Instead of letting __skb_put_padto allocate a new (too small) sk_buff,
> lets take the already existing path and allocate a new sk_buff ourself
> (with sufficient size).

Hi Christian

What is not clear to me is why not change the __skb_put_padto() call
to pass the correct length?

   Andrew