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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <435477a4-bf2d-f710-a1a0-f1957eb01f7a@gmail.com>
Date:   Wed, 21 Mar 2018 08:26:20 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yonghong Song <yhs@...com>, edumazet@...gle.com, ast@...com,
        daniel@...earbox.net, diptanu@...com, netdev@...r.kernel.org
Cc:     kernel-team@...com
Subject: Re: [PATCH net-next v4 2/2] net: bpf: add a test for skb_segment in
 test_bpf module



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;
> +}
> +