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).
I won't claim to know this code nor what the proper fix is; just thought
i'd report it so someone else with more knowledge of this could perhaps
come up with a fix.
Have a nice day.
--
Jesper Juhl <[email protected]> http://www.chaosbits.net/
Don't top-post http://www.catb.org/jargon/html/T/top-post.html
Plain text mails only, please.
On Thu, 16 Jun 2011, Connor Hansen wrote:
> On Thu, Jun 16, 2011 at 3:06 PM, Jesper Juhl <[email protected]> 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 <[email protected]> http://www.chaosbits.net/
Don't top-post http://www.catb.org/jargon/html/T/top-post.html
Plain text mails only, please.
On Thu, Jun 16, 2011 at 3:06 PM, Jesper Juhl <[email protected]> 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.
static void rollback_registered(struct net_device *dev)
{
LIST_HEAD(single);
list_add(&dev->unreg_list, &single); null dereference
rollback_registered_many(&single);
list_del(&single);
}
static void net_set_todo(struct net_device *dev)
{
list_add_tail(&dev->todo_list, &net_todo_list); null dereference
}
Connor
>
> I won't claim to know this code nor what the proper fix is; just thought
> i'd report it so someone else with more knowledge of this could perhaps
> come up with a fix.
>
> Have a nice day.
>
> --
> Jesper Juhl <[email protected]> ? ? ? http://www.chaosbits.net/
> Don't top-post http://www.catb.org/jargon/html/T/top-post.html
> Plain text mails only, please.
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at ?http://www.tux.org/lkml/
>