linux-kernel - Re: [GIT PULL] Asymmetric keys fix for v6.4-rc5

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Message-ID: <CAHk-=wj4S0t5RnJQmF_wYwv+oMTKggwdLnrA9D1uMNKq4H4byw@mail.gmail.com>
Date:   Fri, 2 Jun 2023 13:38:26 -0400
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biggers <ebiggers@...nel.org>,
        Stefan Berger <stefanb@...ux.ibm.com>, davem@...emloft.net,
        zohar@...ux.ibm.com, dmitry.kasatkin@...il.com,
        paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com,
        Jarkko Sakkinen <jarkko@...nel.org>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [GIT PULL] Asymmetric keys fix for v6.4-rc5

On Fri, Jun 2, 2023 at 10:41 AM Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
>
> sorry for this unusual procedure of me requesting a patch to be pulled.
> I asked for several months the maintainers (David: asymmetric keys,
> Jarkko: key subsystem) to pick my patch but without any luck.

Hmm.

The patch behind that tag looks sane to me, but this is not code I am
hugely familiar with.

Who is the caller that passes in the public_key_signature data on the
stack to public_key_verify_signature()? This may well be the right
point to move it away from the stack in order to have a valid sg-list,
but even if this patch is all good, it would be nice to have the call
chain documented as part of the commit message.

> I signed the tag, but probably it would not matter, since my key is not
> among your trusted keys.

It does matter - I do pull from people even without full chains, I
just end up being a lot more careful, and I still want to see the
signature for any future reference...

DavidH, Herbert, please comment:

>   https://github.com/robertosassu/linux.git tags/asym-keys-fix-for-linus-v6.4-rc5

basically public_key_verify_signature() is passed that

     const struct public_key_signature *sig

as an argument, and currently does

        sg_init_table(src_sg, 2);
        sg_set_buf(&src_sg[0], sig->s, sig->s_size);
        sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);

on it which is *not* ok if the s->s and s->digest points to stack data
that ends up not dma'able because of a virtually mapped stack.

The patch re-uses the allocation it already does for the key data, and
it seems sane.

But again, this is not code I look at normally, so...

               Linus