From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754444Ab1HBMld (ORCPT ); Tue, 2 Aug 2011 08:41:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52352 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754255Ab1HBMl2 (ORCPT ); Tue, 2 Aug 2011 08:41:28 -0400 Date: Tue, 2 Aug 2011 08:41:18 -0400 From: Josh Boyer To: Adam Cozzette Cc: edwin_rong , wwang , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: ums-realtek driver uses stack memory for DMA Message-ID: <20110802124117.GH2096@zod.bos.redhat.com> References: <20110801210905.GC2096@zod.bos.redhat.com> <20110802050411.GC3857@[192.168.0.12]> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20110802050411.GC3857@[192.168.0.12]> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 01, 2011 at 11:04:11PM -0600, Adam Cozzette wrote: > On Mon, Aug 01, 2011 at 05:09:06PM -0400, Josh Boyer wrote: > > Hello, > > > > We have a report that the ums-realtek driver is generating a backtrace > > due to using stack variables for DMA buffers. The backtrace is below > > and you can view the bug report here: > > https://bugzilla.redhat.com/show_bug.cgi?id=720054 > > > > Looking through the code, it seems that every call to rts51x_read_mem, > > rts51x_write_mem, and rts51x_read_status passes a stack variable to > > rts51x_bulk_transport, which then calls usb_stor_bulk_transfer_buf with > > this and generates the backtrace. It is my understanding that the > > driver should be passing variables that are not on the stack and have > > been allocated with memory that will be suitable for the DMA api (e.g. > > kmalloc). > > > > Was this missed during the initial review and is anyone working on > > adapting the driver to be compliant? > > Could you try out this patch if it looks ok to you? I have not tested it because > unfortunately I don't have the hardware. Right now it generates some compile > warnings like this one: > > drivers/usb/storage/realtek_cr.c:419:40: warning: ‘buf[0]’ may be used uninitialized in this function [-Wuninitialized] > > It think they are harmless but I didn't see an obvious way to get rid of them, > so if you have any suggestions I would be glad to hear them. > > This patch changed rts51x_read_mem, rts51x_write_mem, and rts51x_read_status to > allocate temporary buffers with kmalloc. This way stack addresses are not used > for DMA when these functions call rts51x_bulk_transport. > > Signed-off-by: Adam Cozzette This looks pretty good. I backported it to 3.0 and will do a scratch build for the bug reporter to test with. josh