netdev - Re: Sending short raw packets using sendmsg() broke

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Date:	Fri, 04 Mar 2016 15:54:09 +0000
From:	Alan Cox <alan@...ux.intel.com>
To:	Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Heikki Hannikainen <hessu@....iki.fi>,
	Network Development <netdev@...r.kernel.org>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: Sending short raw packets using sendmsg() broke

> > A quick search for ethhdr in drivers/net/ethernet shows, for
> > instance,
> > bnx2x_select_queue casting skb->data to an ethernet header. Reading
> > nonsense in that particular function is quite safe and given the
> > skbuff layout (skb_shared_info) code will never read beyond an
> > allocated region. But that was just the first occurrence I found.
> > efx_tso_check_protocol is another example.

So would always allocating that much space be a good mitigation in
general, and perhaps then making the logic check validate() IFF
CAP_SYS_RAWIO is not set.

A user with CAP_SYS_RAWIO already has the power to control the device
by banging registers so the check is not a security loss.

Alan