linux-kernel - Re: [PATCH v2] Bluetooth: 6LoWPAN: Add missing check for skb

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Date:   Fri, 17 Mar 2023 22:03:21 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     marcel@...tmann.org, johan.hedberg@...il.com, luiz.dentz@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, linux-bluetooth@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: 6LoWPAN: Add missing check for skb_clone

On Wed, Mar 15, 2023 at 03:06:21PM +0800, Jiasheng Jiang wrote:
> Add the check for the return value of skb_clone since it may return NULL
> pointer and cause NULL pointer dereference in send_pkt.
> 
> Fixes: 18722c247023 ("Bluetooth: Enable 6LoWPAN support for BT LE devices")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog:
> 
> v1 -> v2:
> 
> 1. Modify the error handling in the loop.

I think that at a minimum this needs to be included in the patch description.
Or better, in it's own patch with it's own fixes tag.
It seems like a fundamental change to the error handling to me.

> ---
>  net/bluetooth/6lowpan.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
> index 4eb1b3ced0d2..55ae2ff40efb 100644
> --- a/net/bluetooth/6lowpan.c
> +++ b/net/bluetooth/6lowpan.c
> @@ -477,19 +477,25 @@ static int send_mcast_pkt(struct sk_buff *skb, struct net_device *netdev)
>  			int ret;
>  
>  			local_skb = skb_clone(skb, GFP_ATOMIC);
> +			if (!local_skb) {
> +				err = -ENOMEM;
> +				goto out;
> +			}
>  
>  			BT_DBG("xmit %s to %pMR type %u IP %pI6c chan %p",
>  			       netdev->name,
>  			       &pentry->chan->dst, pentry->chan->dst_type,
>  			       &pentry->peer_addr, pentry->chan);
>  			ret = send_pkt(pentry->chan, local_skb, netdev);
> -			if (ret < 0)
> -				err = ret;
> -
>  			kfree_skb(local_skb);
> +			if (ret < 0) {
> +				err = ret;
> +				goto out;
> +			}
>  		}
>  	}
>  
> +out:
>  	rcu_read_unlock();
>  
>  	return err;
> -- 
> 2.25.1
>