Re: [PATCH v4 1/2] drivers: net: prevent tun_build_skb() to exceed the packet size limit

[David Ahern]

On 8/1/23 4:07 PM, Andrew Kanner wrote:
> @@ -1594,7 +1597,13 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
>  	if (zerocopy)
>  		return false;
>  
> -	if (SKB_DATA_ALIGN(len + TUN_RX_PAD) +
> +	rcu_read_lock();
> +	xdp_prog = rcu_dereference(tun->xdp_prog);
> +	if (xdp_prog)
> +		pad += XDP_PACKET_HEADROOM;
> +	rcu_read_unlock();


since you do not care about the actual xdp_prog (only that one is set) I
believe you can use rcu_access_pointer here.