netdev - Re: [PATCH] net: fix a concurrency bug in l2tp_tunnel

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: <20210428124534.6f1d7dc4@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 28 Apr 2021 12:45:34 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Gong, Sishuai" <sishuai@...due.edu>
Cc:     David Miller <davem@...emloft.net>,
        "tparkin@...alix.com" <tparkin@...alix.com>,
        Matthias Schiffer <mschiffer@...verse-factory.net>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: fix a concurrency bug in l2tp_tunnel_register()

On Tue, 27 Apr 2021 15:04:24 +0000 Gong, Sishuai wrote:
> l2tp_tunnel_register() registers a tunnel without fully
> initializing its attribute. This can allow another kernel thread
> running l2tp_xmit_core() to access the uninitialized data and
> then cause a kernel NULL pointer dereference error, as shown below.
> 
> Thread 1    Thread 2
> //l2tp_tunnel_register()
> list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
>            //pppol2tp_connect()
>            tunnel = l2tp_tunnel_get(sock_net(sk), info.tunnel_id);
>            // Fetch the new tunnel
>            ...
>            //l2tp_xmit_core()
>            struct sock *sk = tunnel->sock;
>            ...
>            bh_lock_sock(sk);
>            //Null pointer error happens
> tunnel->sock = sk;
> 
> Fix this bug by initializing tunnel->sock before adding the
> tunnel into l2tp_tunnel_list.
> 
> Reviewed-by: Cong Wang <cong.wang@...edance.com>
> Signed-off-by: Sishuai Gong <sishuai@...due.edu>
> Reported-by: Sishuai Gong <sishuai@...due.edu>

Thanks for the patch! Unfortunately the patch in the email is
corrupted, looks like something removed spaces at the start of 
the lines which are expected in patches, e.g.:

»       pn·=·l2tp_pernet(net);$
$
+»      sk·=·sock->sk;$

Should have been:

 »      pn·=·l2tp_pernet(net);$
 $
+»      sk·=·sock->sk;$

Could you try to resend once more with git-send-email or via 
a different mail server?