netdev - Re: kernel BUG at net/core/skbuff.c:95!

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Message-Id: <20080220.215707.194209573.davem@davemloft.net>
Date:	Wed, 20 Feb 2008 21:57:07 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	jwestfall@...realistic.net
Cc:	netdev@...r.kernel.org, acme@...stprotocols.net
Subject: Re: kernel BUG at net/core/skbuff.c:95!

From: Jim Westfall <jwestfall@...realistic.net>
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:

1) First this function validates that there are really
   'dsize' bytes available in the ev_skb source.

2) Second, skb_realloc_headroom() is called on 'skb' with
   a second argument of 'dsize'.

That means also this function now needs to return error
values, and the callers updated to handle that.
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