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Date:   Tue, 18 Jan 2022 16:59:47 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Jarkko Sakkinen <jarkko@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: <Yedigyl+WNhB58MO@sol.localdomain>
References: <20220113235440.90439-1-ebiggers@kernel.org>
 <20220113235440.90439-2-ebiggers@kernel.org>
 <YeM/YIUTEwL4jNf3@iki.fi>
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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.

- Eric