linux-kernel - Re: DMA debug trace pointing to rtl8187

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Message-ID: <20090509192959.GA1842@kroah.com>
Date:	Sat, 9 May 2009 12:29:59 -0700
From:	Greg KH <greg@...ah.com>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	Eric Valette <eric.valette@...e.fr>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, Hin-Tak Leung <hintak.leung@...il.com>
Subject: Re: DMA debug trace pointing to rtl8187

On Sat, May 09, 2009 at 12:29:27PM -0500, Larry Finger wrote:
> I think there is a second problem that John's fix does not treat. Although the
> buffer is removed from the stack, there is no assurance that the buffer obtained
> with kmalloc() is reachable by DMA. This case will be triggered if the USB
> adapter does 32-bit DMA and the system has more than 4 GB RAM.

Memory returned by kmalloc will always be able to be DMAable.  If not,
we have lots of problems :)

thanks,

greg k-h
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