linux-kernel - Re: rionet: NULL pointer dereference

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Message-ID: <alpine.LNX.2.00.1106170050180.8140@swampdragon.chaosbits.net>
Date:	Fri, 17 Jun 2011 00:51:59 +0200 (CEST)
From:	Jesper Juhl <jj@...osbits.net>
To:	Connor Hansen <cmdkhh@...il.com>
cc:	linux-kernel@...r.kernel.org,
	Matt Porter <mporter@...nel.crashing.org>,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: rionet: NULL pointer dereference

On Thu, 16 Jun 2011, Connor Hansen wrote:

> On Thu, Jun 16, 2011 at 3:06 PM, Jesper Juhl <jj@...osbits.net> wrote:
> > Hi
> >
> > Just noticed that drivers/net/rionet.c::rionet_remove() can cause a NULL
> > deref when it calls unregister_netdev().
> > It initializes local variable 'ndev' to NULL and nothing changes this
> > before the call to unregister_netdev(ndev) - that functions then calls:
> > unregister_netdevice > unregister_netdevice_queue > list_move_tail >
> > __list_del_entry  which dereferences the pointer (which, being NULL, will
> > end in tears).
> 
> unregister_netdevice(struct net_device *dev)
> {
>         unregister_netdevice_queue(dev, NULL);
> }
> 
>  so unregister_netdevice_queue is being called with NULL,NULL
> 
> void unregister_netdevice_queue(struct net_device *dev, struct list_head *head)
> {
>         ASSERT_RTNL();
> 
>         if (head) {
>                 list_move_tail(&dev->unreg_list, head);
>         } else {
>                 rollback_registered(dev);
>                 /* Finish processing unregister after unlock */
>                 net_set_todo(dev);
>         }
> }
> 
> if head is null, which it is from the call, then we call
> rollback_registered, and not list_move_tail()
> 
> the else calls rollback_registered(NULL) then net_set_todo(NULL)
> 
> both of which dereference null when passed, so yes there is a null
> dereference, just not in the code branch you thought.
> 

Ahh crap, you are right. Too much coffee and too late to be reading kernel 
code is my only excuse ;-)
Thanks for taking the time to look and correct me.


In any case, there's still a problem that needs to be fixed.

-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
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