linux-kernel - Re: [PATCH 0/6] get rid of on-stack dma buffers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:	Tue, 22 Mar 2011 14:12:46 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Florian Mickler <florian@...kler.org>
Cc:	"Roedel, Joerg" <Joerg.Roedel@....com>,
	"Greg Kroah-Hartman" <greg@...ah.com>,
	"janne-dvb@...nau.be" <janne-dvb@...nau.be>,
	"g.marco@...enet.de" <g.marco@...enet.de>,
	"tskd2@...oo.co.jp" <tskd2@...oo.co.jp>,
	"liplianin@...by" <liplianin@...by>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"pb@...uxtv.org" <pb@...uxtv.org>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"max@...eto.com" <max@...eto.com>,
	"mchehab@...radead.org" <mchehab@...radead.org>,
	"aet@...terburn.org" <aet@...terburn.org>,
	"mkrufky@...uxtv.org" <mkrufky@...uxtv.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	"js@...uxtv.org" <js@...uxtv.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andy Walls <awalls@...metrocast.net>,
	"nick@...k-andrew.net" <nick@...k-andrew.net>
Subject: Re: [PATCH 0/6] get rid of on-stack dma buffers

Am Dienstag, 22. März 2011, 14:08:17 schrieb Florian Mickler:
> Am 22.03.2011 12:10 schrieb "Roedel, Joerg" <Joerg.Roedel@....com>:
> >
> > On Mon, Mar 21, 2011 at 05:03:15PM -0400, Florian Mickler wrote:
> > > I guess (not verified), that the dma api takes sufficient precautions
> > > to abort the dma transfer if a timeout happens.  So freeing _should_
> > > not be an issue. (At least, I would expect big fat warnings everywhere
> > > if that were the case)
> >
> > Freeing is very well an issue. All you can expect from the DMA-API is to
> > give you a valid DMA handle for your device. But it can not prevent that
> > a device uses this handle after you returned it. You need to make sure
> > yourself that any pending DMA is canceled before calling kfree().
> 
> Does usb_control_msg do this? It waits for completion but takes also a
> timeout parameter. I will recheck this once I'm home.

It uses usb_start_wait_urb() which upon a timeout kills the URB. The
buffer is unused after usb_control_msg() returns.

	HTH
		Oliver
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/