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Date:   Wed, 26 Jan 2022 16:21:50 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     keyrings@vger.kernel.org, David Howells <dhowells@redhat.com>,
        Denis Kenzior <denkenz@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        James Morris <james.morris@microsoft.com>,
        linux-crypto@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 1/3] KEYS: asym_tpm: fix buffer overreads in
 extract_key_parameters()
Message-ID: <YfFY/trrVl3vse5I@iki.fi>
References: <20220113235440.90439-1-ebiggers@kernel.org>
 <20220113235440.90439-2-ebiggers@kernel.org>
 <YeM/YIUTEwL4jNf3@iki.fi>
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On Tue, Jan 18, 2022 at 04:59:47PM -0800, Eric Biggers wrote:
> On Sat, Jan 15, 2022 at 11:40:48PM +0200, Jarkko Sakkinen wrote:
> > > 
> > > - Avoid integer overflows when validating size fields; 'sz + 12' and
> > >   '4 + sz' overflowed if 'sz' is near U32_MAX.
> > 
> > So we have a struct tpm_header in include/linux/tpm.h. It would be way
> > more informative to use sizeof(struct tpm_header) than number 12, even
> > if the patch does not otherwise use the struct. It tells what it is, 12
> > does not.
> 
> I don't think that would be an improvement, given that the code is using
> hard-coded offsets.  If it's reading 4 bytes from cur + 8, it's much easier to
> understand that it needs 12 bytes than 'sizeof(struct tpm_header)' bytes.
> 
> I'd certainly encourage whoever is maintaining this code to change it to use
> structs instead, but that's not what this patch is meant to do.

I would consider dropping asym_tpm as it has no practical use cases
existing.

/Jarkko