netdev - Re: [PATCHv2 net 3/3] net: sched: ife: check on metadata length

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Message-ID: <2cd6cb29-ab28-bd99-4fbd-a4f5659e3009@gmail.com>
Date:   Thu, 19 Apr 2018 14:50:27 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexander Aring <aring@...atatu.com>, yotam.gi@...il.com
Cc:     jhs@...atatu.com, davem@...emloft.net, xiyou.wangcong@...il.com,
        jiri@...nulli.us, yuvalm@...lanox.com, netdev@...r.kernel.org,
        kernel@...atatu.com
Subject: Re: [PATCHv2 net 3/3] net: sched: ife: check on metadata length



On 04/19/2018 02:44 PM, Alexander Aring wrote:
> This patch checks if sk buffer is available to dererence ife header. If
> not then NULL will returned to signal an malformed ife packet. This
> avoids to crashing the kernel from outside.
> 
> Signed-off-by: Alexander Aring <aring@...atatu.com>
> Reviewed-by: Yotam Gigi <yotam.gi@...il.com>
> Acked-by: Jamal Hadi Salim <jhs@...atatu.com>
> ---
>  net/ife/ife.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ife/ife.c b/net/ife/ife.c
> index 7fbe70a0af4b..93e8c36ce6ec 100644
> --- a/net/ife/ife.c
> +++ b/net/ife/ife.c
> @@ -70,6 +70,9 @@ void *ife_decode(struct sk_buff *skb, u16 *metalen)
>  	u16 ifehdrln;
>  
>  	ifehdr = (struct ifeheadr *) (skb->data + skb->dev->hard_header_len);
> +	if (skb->len < skb->dev->hard_header_len + IFE_METAHDRLEN)
> +		return NULL;
> +
>  	ifehdrln = ntohs(ifehdr->metalen);
>  	total_pull = skb->dev->hard_header_len + ifehdrln;
>  
> 

Nope, please use pskb_may_pull()