netdev - Re: [PATCH] net: ipv4: tcp_offload: check segs for NULL

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Message-ID: <1481858921.6603.5.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 15 Dec 2016 19:28:41 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     shakya.das@...sung.com
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        shakya89.das@...il.com, vidushi.koul@...sung.com
Subject: Re: [PATCH] net: ipv4: tcp_offload: check segs for NULL

On Thu, 2016-12-15 at 14:17 +0530, shakya.das@...sung.com wrote:
> From: Shakya Sundar Das <shakya.das@...sung.com>
> 
> This patch will check segs for being NULL in tcp_gso_segment()
> before calling skb_shinfo(segs) from skb_is_gso(segs), otherwise
> kernel can run into a NULL-pointer dereference.
> 
> Signed-off-by: Shakya Sundar Das <shakya.das@...sung.com>
> ---
>  net/ipv4/tcp_offload.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index bc68da3..93feefd 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -96,7 +96,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
>  	skb->ooo_okay = 0;
>  
>  	segs = skb_segment(skb, features);
> -	if (IS_ERR(segs))
> +	if (IS_ERR_OR_NULL(segs))
>  		goto out;
>  
>  	/* Only first segment might have ooo_okay set */

I do not see how this can ever happen.

How did you come up with this patch exactly ???