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From: Sven Eckelmann <sven.eckelmann@gmx.de>
To: b.a.t.m.a.n@lists.open-mesh.org
Subject: Re: [B.A.T.M.A.N.] [PATCH] drivers/staging/batman-adv: Use (pr|netdev)_<level> macro helpers
Date: Wed, 16 Jun 2010 00:37:47 +0200
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Cc: devel <devel@driverdev.osuosl.org>, b.a.t.m.a.n@lists.open-mesh.net,
       "Greg Kroah-Hartman" <gregkh@suse.de>, linux-kernel@vger.kernel.org,
       Simon Wunderlich <siwu@hrz.tu-chemnitz.de>,
       Joe Perches <joe@perches.com>, Marek Lindner <lindner_marek@yahoo.de>
References: <1275498615.23599.12.camel@Joe-Laptop.home> <1275509466.23599.43.camel@Joe-Laptop.home> <201006160023.04296.sven.eckelmann@gmx.de>
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Sven Eckelmann wrote:
[...]
> Found some time to play a little bit around with your patch and noticed
> that it crashes the kernel. I did my tests using following "interesting"
> part:
>=20
[...]
>=20
> I compiled the module and loaded it using `insmod batman-adv.ko`. This wi=
ll
> create some files in /sys. Just changed the vis mode to server using:
>=20
> echo 0 > /sys/class/net/bat0/mesh/vis_mode
>=20
> And then it will crash at that netdev_info call.
>=20
> The problem seems to be that dev_printk is used by netdev_printk (which is
> used by netdev_info). netdev_printk will add (netdev)->dev.parent as seco=
nd
> parameter of dev_printk (and parent is NULL in our case). This macro will
> now call dev_driver_string with NULL as parameter and just dereference
> this null pointer.
>=20
> Maybe it is related to something else, but at least I think that this cou=
ld
> be the cause of the crash.

Something i forgot to say:

As far as I understand, the netdev_* stuff is made to be used by real drive=
rs=20
with more or less physical hardware. batman-adv is a virtual bridge used fo=
r=20
mesh networks. Like net/bridge/ it has no physical parent device and only=20
other net_devices are used inside of it - which may have real physical netw=
ork=20
devices as parents.

Please correct me if my assumption is wrong.

Best regards,
	Sven

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