linux-kernel - Re: [PATCH] /dev/mem: handle out-of-bounds read/write

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Date:	Thu, 30 Jan 2014 07:04:07 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Petr Tesarik <ptesarik@...e.cz>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] /dev/mem: handle out-of-bounds read/write

On Thu, Jan 30, 2014 at 03:03:32PM +0100, Petr Tesarik wrote:
> On Thu, 30 Jan 2014 05:28:27 -0800
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> > On Thu, Jan 30, 2014 at 09:48:02AM +0100, Petr Tesarik wrote:
> > > The loff_t type may be wider than phys_addr_t (e.g. on 32-bit systems).
> > > Consequently, the file offset may be truncated in the assignment.
> > > Currently, /dev/mem wraps around, which may cause applications to read
> > > or write incorrect regions of memory by accident.
> > 
> > Does that really happen?  If so, that's a userspace bug, right?
> 
> In my case, it was a userspace bug, indeed. But debugging would have
> been much easier if I saw read() fail with an EOF condition, rather
> than pretend that it actually read some bytes (from above 4G) on a
> 32-bit box.

Thats true.

Ok, I'll queue this up after 3.14-rc1 is out, thanks.

greg k-h
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