netdev - Re: [Socketcan-users] [PATCH] CAN: make checking in can

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Message-Id: <200908070952.56922.remi.denis-courmont@nokia.com>
Date:	Fri, 7 Aug 2009 09:52:56 +0300
From:	"Rémi Denis-Courmont" 
	<remi.denis-courmont@...ia.com>
To:	ext Oliver Hartkopp <oliver@...tkopp.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:	Luotao Fu <l.fu@...gutronix.de>,
	"socketcan-users@...ts.berlios.de" <socketcan-users@...ts.berlios.de>,
	Michael Olbrich <m.olbrich@...gutronix.de>
Subject: Re: [Socketcan-users] [PATCH] CAN: make checking in can_rcv less restrictive

Moving to netdev....

On Thursday 06 August 2009 19:48:23 ext Oliver Hartkopp wrote:
> The CAN applications can rely on getting proper CAN frames with this check.
> It was introduced some time ago together with several other sanity checks -
> even on the TX path.
>
> The CAN core *only* consumes skbuffs originated from a CAN netdevice
> (ARPHRD_CAN).
>
> When this BUG() triggers, someone provided a definitely broken *CAN*
> network driver, and this needs to be fixed on that level. It is really not
> that problematic to ensure proper CAN frames on driver level ... this
> sanity check should not be needed to be performed by every single
> application.

AFAIK, the TUN driver can inject layer-2 frames of any type, any size and any 
content from userspace into the packet type handler. Sure enough, you need 
CAP_NET_ADMIN and r/w access to /dev/net/tun but is it sufficient to bring the 
system down?

-- 
Rémi Denis-Courmont
Nokia Devices R&D, Maemo Software, Helsinki

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