Return-path: Received: from kroah.org ([198.145.64.141]:51450 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753270AbZEITdt (ORCPT ); Sat, 9 May 2009 15:33:49 -0400 Date: Sat, 9 May 2009 12:29:59 -0700 From: Greg KH To: Larry Finger Cc: Eric Valette , FUJITA Tomonori , "John W. Linville" , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Hin-Tak Leung Subject: Re: DMA debug trace pointing to rtl8187 Message-ID: <20090509192959.GA1842@kroah.com> References: <49FDB9F8.3080400@free.fr> <20090506133131F.fujita.tomonori@lab.ntt.co.jp> <4A012FC8.3020304@free.fr> <20090506064513.GA7460@kroah.com> <4A05BD77.9020003@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <4A05BD77.9020003@lwfinger.net> Sender: linux-wireless-owner@vger.kernel.org List-ID: 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