kernel-hardening - Re: [PATCH] gcc-plugins: Add structleak for more stack initialization

Follow @Openwall on Twitter for new release announcements and other news

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

Date: Wed, 18 Jan 2017 10:48:58 +0000
From: Mark Rutland <mark.rutland@....com>
To: PaX Team <pageexec@...email.hu>
Cc: kernel-hardening@...ts.openwall.com, Kees Cook <keescook@...omium.org>,
	Emese Revfy <re.emese@...il.com>,
	"AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
	park jinbum <jinb.park7@...il.com>,
	Daniel Micay <danielmicay@...il.com>, linux-kernel@...r.kernel.org,
	spender@...ecurity.net
Subject: Re: [PATCH] gcc-plugins: Add structleak for more stack initialization

On Tue, Jan 17, 2017 at 07:54:38PM +0100, PaX Team wrote:
> On 17 Jan 2017 at 17:48, Mark Rutland wrote:
> > That being the case, (and given the relevant bug has now been fixed),
> > it's not clear to me what the value of this is today. i.e. given the
> > general case, is this preventing many leaks?
> 
> no idea, i stopped looking at the instrumentation log long ago, but everyone
> can enable the debug output (has a very specific comment on it ;) and look at
> the results. i keep this plugin around because it costs nothing to maintain
> it and the alternative (better) solution doesn't exist yet.

Fair enough; understood.

> > > i never went into that direction because i think the security goal can
> > > be achieved without the performance impact of forced initialization.
> > 
> > Was there a particular technique you had in mind?
> 
> sure, i mentioned it in my SSTIC'12 keynote (page 36):
> https://pax.grsecurity.net/docs/PaXTeam-SSTIC12-keynote-20-years-of-PaX.pdf

Thanks for the pointer.

I'm probably being very naive here, but IIUC the per-task usercopy stack
would require roughly the same analysis to identify relevant variables,
unless all local variables (regardless of initialisation) that fed into
a usercopy would be on the usercopy stack?

Regardless, I can see the benefit of cleanly separating that data from
the rest of the kernel data.

Thanks,
Mark.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.