netdev - Re: [PATCH RESEND] dm9601: don't do usb transfers of data on stack

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Date:	Fri, 11 Jul 2008 14:00:37 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Peter Korsgaard <jacmet@...site.dk>
Cc:	jeff@...zik.org, netdev@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH RESEND] dm9601: don't do usb transfers of data on stack

Am Freitag 11 Juli 2008 13:37:39 schrieb Peter Korsgaard:
> dm_{read,write}_shared_word() were doing USB transfers of data on stack,
> which isn't allowed. Fix it by using the usbnet->data area like in
> dm9601_set_multicast().

You cannot do this. You've identified the bug correctly, but the fix
is incorrect. Doing DMA on non coherent architectures means that
any cacheline the buffer shares must not be touched while DMA
may be running. If you embed the buffer into struct usbnet, how could
you meet the guarantee?

	Regards
		Oliver
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