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Message-ID: <5182.1467104864@warthog.procyon.org.uk>
Date: Tue, 28 Jun 2016 10:07:44 +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:
> Huh? If you can't write to csum_iv_head without clobbering others
> then by the same reasoning you can't write to csum_iv either. So
> unless you're saying the existing code is already broken then there
> is nothing wrong with the patch.
Ah, for some reason I read it as being in the normal packet processing. Need
tea before I read security patches;-)
Since it's (more or less) a one off piece of memory, why not kmalloc it
temporarily rather than expanding the connection struct? Also, the bit where
you put a second rxrpc_crypt in just so that it happens to give you a 16-byte
slot by adjacency is pretty icky. It would be much better to use a union
instead:
union {
struct rxrpc_crypt csum_iv; /* packet checksum base */
__be32 tmpbuf[4];
};
Note also that the above doesn't guarantee that the struct will be inside of a
single page. It would need an alignment of 16 for that - but you only have
one sg. Could that be a problem?
David
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