linux-kernel - Re: ums-realtek driver uses stack memory for DMA

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Date:	Mon, 1 Aug 2011 14:16:59 -0700
From:	Greg KH <gregkh@...e.de>
To:	Josh Boyer <jwboyer@...hat.com>
Cc:	edwin_rong <edwin_rong@...lsil.com.cn>,
	wwang <wei_wang@...lsil.com.cn>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: ums-realtek driver uses stack memory for DMA

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).

That is correct.

> Was this missed during the initial review and is anyone working on
> adapting the driver to be compliant?

Odds are it was missed.  Patches gladly accepted.

thanks,

greg k-h
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