Re: [PATCH net-next v4 2/2] net: bpf: add a test for skb_segment in test_bpf module

[Eric Dumazet <eric.dumazet@gmail.com>]

On 03/20/2018 11:47 PM, Yonghong Song wrote:
> +static __init int test_skb_segment(void)
> +{
> +	netdev_features_t features;
> +	struct sk_buff *skb;
> +	int ret = -1;
> +
> +	features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM |
> +		   NETIF_F_IPV6_CSUM;
> +	features |= NETIF_F_RXCSUM;
> +	skb = build_test_skb();
> +	if (!skb) {
> +		pr_info("%s: failed to build_test_skb", __func__);
> +		goto done;
> +	}
> +
> +	if (skb_segment(skb, features)) {
> +		ret = 0;
> +		pr_info("%s: success in skb_segment!", __func__);
> +	} else {
> +		pr_info("%s: failed in skb_segment!", __func__);
> +	}
> +	kfree_skb(skb);

If skb_segmen() was successful (original) skb was already freed.

kfree_skb(old_skb) should thus panic the box, if you run this code
on a kernel having some debugging features like KASAN

So you must store in a variable the return of skb_segment(),
to be able to free skb(s), using kfree_skb_list()


> +done:
> +	return ret;
> +}
> +