David Miller <[EMAIL PROTECTED]> wrote [02.20.08]:
> From: Jim Westfall <[EMAIL PROTECTED]>
> Date: Wed, 20 Feb 2008 21:46:48 -0800
>
> > static inline void llc_pdu_init_as_test_rsp(struct sk_buff *skb,
> > struct sk_buff *ev_skb)
> > {
> > struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
> >
> > pdu->ctrl_1 = LLC_PDU_TYPE_U;
> > pdu->ctrl_1 |= LLC_1_PDU_CMD_TEST;
> > pdu->ctrl_1 |= LLC_U_PF_BIT_MASK;
> > if (ev_skb->protocol == htons(ETH_P_802_2)) {
> > struct llc_pdu_un *ev_pdu = llc_pdu_un_hdr(ev_skb);
> > int dsize;
> >
> > dsize = ntohs(eth_hdr(ev_skb)->h_proto) - 3;
> > memcpy(((u8 *)pdu) + 3, ((u8 *)ev_pdu) + 3, dsize);
> > skb_put(skb, dsize);
> > }
> > ..
> > }
>
> Probably what should happen is:
>
I just started looking at the skbuff|net|llc code last night, hopefully
these aren't totally stupid questions/comments.
> 1) First this function validates that there are really
> 'dsize' bytes available in the ev_skb source.
looks like this can be done easily with skb_tailroom()..
I am curious if we should also be verifying that dsize is valid? Its
value is coming from a recv'd llc packet.
The llc header is |mac|mac|16bit length|. The above code seems to be
piggy backing a normal ethernet header struct, by using h_proto as the
llc length. I am not sure if that length value can be trusted and we run
the risk of memcpy'ing off the end of the source structure/skbuff?
>
> 2) Second, skb_realloc_headroom() is called on 'skb' with
> a second argument of 'dsize'.
This suggestion escapes me. The skb_put() call in the above
code would increase skb->tail. Wont skb_realloc_headroom() create
additional space between skb->head and skb->data when we really want it
between skb->tail and skb->end?
thanks
jim
>
> That means also this function now needs to return error
> values, and the callers updated to handle that.
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