Re: [net v3] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len

[Xie He]

On Tue, Aug 4, 2020 at 10:23 PM Martin Schiller <ms@xxxxxxxxxx> wrote:
>
> > Adding skb_cow before these skb_push calls would indeed help
> > preventing kernel panics, but that might not be the essential issue
> > here, and it might also prevent us from discovering the real issue. (I
> > guess this is also the reason skb_cow is not included in skb_push
> > itself.)
>
> Well, you are right that the panic is "useful" to discover the real
> problem. But on the other hand, if it is possible to prevent a panic, I
> think we should do so. Maybe with adding a warning, when skb_cow() needs
> to reallocate memory.
>
> But this is getting a little bit off topic. For this patch I can say:
>
> LGTM.
>
> Reviewed-by: Martin Schiller <ms@xxxxxxxxxx>

Thank you so much!

Yes, it might be better to use skb_cow with a warning so that we can
prevent kernel panic while still being able to discover the problem.
If we want to do this, there are 2 more places in addition to
lapbeth_data_transmit that need to be guarded with skb_cow:
lapb_send_iframe and lapb_transmit_buffer in net/lapb/lapb_out.c.
Maybe we can address this in a separate patch.