Messages in this thread | | | Date | Wed, 05 Aug 2020 07:23:55 +0200 | From | Martin Schiller <> | Subject | Re: [net v3] drivers/net/wan/lapbether: Use needed_headroom instead of hard_header_len |
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On 2020-08-04 21:20, Xie He wrote: > On Tue, Aug 4, 2020 at 5:43 AM Martin Schiller <ms@dev.tdt.de> wrote: >> >> I'm not an expert in the field, but after reading the commit message >> and >> the previous comments, I'd say that makes sense. > > Thanks! > >> Shouldn't this kernel panic be intercepted by a skb_cow() before the >> skb_push() in lapbeth_data_transmit()? > > When a skb is passing down a protocol stack for transmission, there > might be several different skb_push calls to prepend different > headers. It would be the best (in terms of performance) if we can > allocate the needed header space in advance, so that we don't need to > reallocate the skb every time a new header needs to be prepended.
Yes, I agree.
> 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@dev.tdt.de>
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