linux-kernel - Re: [GIT PULL] char/misc driver patches for 3.16-rc1

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Date:	Tue, 3 Jun 2014 10:14:41 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Bin Wang <binw@...vell.com>,
	Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@...esas.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] char/misc driver patches for 3.16-rc1

On Tue, Jun 3, 2014 at 10:02 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
>
> Hm, I got two different bug reports, and this same patch from two
> different people insisting that we broke their drivers with the above
> patches, and asked for this patch to be applied.

So I do think that we might be able to apply this patch, but I think
it needs a *lot* more thought than was obviously spent on it so far.

For example, right now it's actively insecure. Do we care? Maybe we
don't. The user-space uio side presumably is root-owned, and hopefully
trusted.

And what about the unaligned mmio case? Are people somehow
guaranteeing that the regions is page-aligned, even if it isn't
page-sized?

What is the actual hardware in question?

Basically, it's an obvious security issue, and we shouldn't just say
"whatever". But maybe - with lots of commentary about why the security
implications aren't actually bad in _practice_, and why things are
always page-aligned even if they aren't page-sized, we can say "ok,
it's wrong, but we can still do it because xyz".

So I'm mostly unhappy because I didn't see that kind of analysis, not
because the patch might not eventually be ok. A "this breaks my
driver" is nowhere near the kind of thought this needs, I think.

                 Linus
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