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Message-ID: <20161210060316.GC6846@zzz>
Date: Fri, 9 Dec 2016 22:03:16 -0800
From: Eric Biggers <ebiggers3@...il.com>
To: kernel-hardening@...ts.openwall.com
Cc: Andy Lutomirski <luto@...capital.net>, linux-crypto@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
Andrew Lutomirski <luto@...nel.org>,
Stephan Mueller <smueller@...onox.de>
Subject: Re: Re: Remaining crypto API regressions with
CONFIG_VMAP_STACK
On Sat, Dec 10, 2016 at 01:32:08PM +0800, Herbert Xu wrote:
> On Fri, Dec 09, 2016 at 09:25:38PM -0800, Andy Lutomirski wrote:
> >
> > > The following crypto drivers initialize a scatterlist to point into an
> > > ablkcipher_request, which may have been allocated on the stack with
> > > SKCIPHER_REQUEST_ON_STACK():
> > >
> > > drivers/crypto/ccp/ccp-crypto-aes-xts.c:162
> > > drivers/crypto/ccp/ccp-crypto-aes.c:94
> >
> > These are real, and I wish I'd known about them sooner.
>
> Are you sure? Any instance of *_ON_STACK must only be used with
> sync algorithms and most drivers under drivers/crypto declare
> themselves as async.
>
Why exactly is that? Obviously, it wouldn't work if you returned from the stack
frame before the request completed, but does anything stop someone from using an
*_ON_STACK() request and then waiting for the request to complete before
returning from the stack frame?
Eric
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