netdev - [HELP] ATM: mpc, use-after-free

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-next>] [day] [month] [year] [list]

Message-ID: <4CB2C33C.8080109@gmail.com>
Date:	Mon, 11 Oct 2010 09:56:44 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	"David S. Miller" <davem@...emloft.net>
CC:	ML netdev <netdev@...r.kernel.org>,
	linux-atm-general@...ts.sourceforge.net,
	LKML <linux-kernel@...r.kernel.org>, chas@....nrl.navy.mil
Subject: [HELP] ATM: mpc, use-after-free

Hi,

Stanse found this use-after-free:

static void mpc_push(struct atm_vcc *vcc, struct sk_buff *skb)
{
...
        new_skb = skb_realloc_headroom(skb, eg->ctrl_info.DH_length);

        dev_kfree_skb_any(skb);

FREE    ^^^^^^^^^^^^^^^^^^^^^^^

        if (new_skb == NULL) {
                mpc->eg_ops->put(eg);
                return;
        }
        skb_push(new_skb, eg->ctrl_info.DH_length);
        skb_copy_to_linear_data(new_skb, eg->ctrl_info.DLL_header,
                                eg->ctrl_info.DH_length);
 ...
        memset(ATM_SKB(skb), 0, sizeof(struct atm_skb_data));

USE            ^^^^^^^^^^^^

        netif_rx(new_skb);

I guess it should be ATM_SKB(new_skb), right?

The two problems are:
1) obvious use-after-free
2) ?data leak, since we don't erase the right memory?

thanks,
-- 
js
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html