linux-kernel - Re: [2.6 patch] net/llc/llc_conn.c: fix possible NULL dereference

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Date:	Fri, 18 May 2007 22:30:05 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Eugene Teo <eteo@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [2.6 patch] net/llc/llc_conn.c: fix possible NULL dereference

On Sat, 19 May 2007 13:13:07 +0800 Eugene Teo wrote:

> skb_peek() might return an empty list. skb should be checked before calling
> llc_pdu_sn_hdr() with it.
> 
> Spotted by the Coverity checker.
> 
> Signed-off-by: Eugene Teo <eteo@...hat.com>

Hi Eugene,

Networking patches need to be sent to the netdev@...r.kernel.org
mailing list  (and lkml can be omitted IMHO).

But... instead of doing the assignment and test in one swoop,
we prefer:

>         if (!q_len)
>                 goto out;
>         skb = skb_peek(&llc->pdu_unack_q);
> +       if (!skb)
> +               goto out;
>         pdu = llc_pdu_sn_hdr(skb);

Oh, and your patch has spaces instead of tabs.  It's a hassle to
get thunderbird to send a patch that preserves tabs.  See if this:
   http://mbligh.org/linuxdocs/Email/Clients/Thunderbird
helps you any.


> diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
> index 3b8cfbe..28a3994 100644
> --- a/net/llc/llc_conn.c
> +++ b/net/llc/llc_conn.c
> @@ -323,7 +323,8 @@ int llc_conn_remove_acked_pdus(struct sock *sk, u8 nr, u16
> *how_many_unacked)
> 
>         if (!q_len)
>                 goto out;
> -       skb = skb_peek(&llc->pdu_unack_q);
> +       if (! (skb = skb_peek(&llc->pdu_unack_q)))
> +               goto out;
>         pdu = llc_pdu_sn_hdr(skb);
> 
>         /* finding position of last acked pdu in queue */
> 
> -

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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