linux-kernel - Re: USB mass storage and ARM cache coherency

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

Date:	Wed, 17 Feb 2010 09:55:53 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Oliver Neukum <oliver@...kum.org>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	Matthew Dharm <mdharm-kernel@...-eyed-alien.net>,
	Ming Lei <tom.leiming@...il.com>,
	"Mankad, Maulik Ojas" <x0082077@...com>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>, Greg KH <greg@...ah.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: USB mass storage and ARM cache coherency

On Wed, Feb 17, 2010 at 08:05:43PM +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2010-02-16 at 09:22 +0100, Oliver Neukum wrote:
> > This seems wrong to me. Buffers for control transfers may be
> > transfered
> > by DMA, so the caches must be flushed on architectures whose caches
> > are not coherent with respect to DMA.
> > 
> > Would you care to elaborate on the exact nature of the bug you are
> > fixing?
> 
> I missed part of this thread, so forgive me if I'm a bit off here, but
> if the problem is indeed I$/D$ cache coherency vs. PIO transfers, then
> this is a long solved issue on other archs such as ppc (and I _think_
> sparc).

Nope.  It's to do with mapping a buffer for DMA, and then doing PIO
reads/writes to it.

With speculative prefetches, you have to deal with cache coherency with
hardware DMA on DMA unmap.  If you've written to the buffer in violation
of the DMA API buffer ownership rules, then your writes get thrown away
resulting in immediate data corruption.
--
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/