netdev - Re: [B.A.T.M.A.N.] [PATCH net] net: batman-adv: Fix possible memleaks when fail to register

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Message-ID: <3994535.Z9kqCnttI2@bentobox>
Date:   Wed, 26 Apr 2017 07:57:44 +0200
From:   Sven Eckelmann <sven@...fation.org>
To:     Gao Feng <gfree.wind@...mail.com>
Cc:     b.a.t.m.a.n@...ts.open-mesh.org, mareklindner@...mailbox.ch,
        sw@...onwunderlich.de, a@...table.cc, davem@...emloft.net,
        netdev@...r.kernel.org, 'Gao Feng' <fgao@...ai8.com>
Subject: Re: [B.A.T.M.A.N.] [PATCH net] net: batman-adv: Fix possible memleaks when fail to register_netdevice

On Mittwoch, 26. April 2017 08:41:30 CEST Gao Feng wrote:
> On Dienstag, 25. April 2017 20:03:20 CEST gfree.wind@...mail.com wrote:
> > From: Gao Feng <fgao@...ai8.com>
> > 
> > Because the func batadv_softif_init_late allocate some resources and
> > it would be invoked in register_netdevice. So we need to invoke the
> > func batadv_softif_free instead of free_netdev to cleanup when fail
> > to register_netdevice.
> 
> I could be wrong, but shouldn't the destructor be replaced with free_netdevice 
> and the batadv_softif_free (without the free_netdev) used as ndo_uninit? The 
> line you've changed should then be kept as free_netdevice.
> 
> At least this seems to be important when using rtnl_newlink() instead of the 
> legacy sysfs netdev stuff from batman-adv. rtnl_newlink() would also only call 
> free_netdevice and thus also not run batadv_softif_free. This seems to be only 
> fixable by calling ndo_uninit.
> 
> Sorry, I don't get you.
> The net_dev is created in this func batadv_softif_create.
> Why couldn't invoke batadv_softif_free to cleanup when fail to
> register_netdevice?
> 

Because it is the legacy way to create the batadv interfaces and there is a 
"new" one. The new way is to use rtnl link (see batadv_link_ops). 

The rtnl linke (rtnl_newlink) would not benefit from your fix and therefore 
still show the old behavior. I think a different fix is necessary to solve the 
problem for both ways to create an batadv interface.

Kind regards,
	Sven
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