linux-kernel - Re: [PATCH v4 02/29] rxrpc: Avoid using stack memory in SG lists in rxkad

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Message-ID: <14865.1467108030@warthog.procyon.org.uk>
Date:	Tue, 28 Jun 2016 11:00:30 +0100
From:	David Howells <dhowells@...hat.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	dhowells@...hat.com, Andy Lutomirski <luto@...nel.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v4 02/29] rxrpc: Avoid using stack memory in SG lists in rxkad

Herbert Xu <herbert@...dor.apana.org.au> wrote:

> > I'm using the per-skb state for my own purposes and might be looking at it
> > elsewhere at the same time.
> 
> AFAICS this cannot happen for secure_packet/verify_packet.  In both
> cases we have exclusive ownership of the skb.

In code I'm busy working on the patch I'm decrypting may be on the receive
queue several times.  rxrpc has a jumbo packet concept whereby a packet may be
constructed in such a way that it's actually several packets stitched together
- the idea being that a router can split it up (not that any actually do that
I know of) - but each segment of the jumbo packet may be enqueued as a
separate entity.

> But it's your code so feel free to send your own patch.

I will apply something very similar to my tree.  Andy's patch does not apply
as-is due to conflicts.

David