linux-kernel - Re: [PATCH v2 1/6] crypto: Use memzero

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Message-ID: <20201023204536.GB27708@gondor.apana.org.au>
Date:   Sat, 24 Oct 2020 07:45:36 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        David Laight <David.Laight@...lab.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] crypto: Use memzero_explicit() for clearing state

On Fri, Oct 23, 2020 at 08:56:04AM -0700, Eric Biggers wrote:
>
> When clearing memory because "it may be sensitive" rather than "it's needed for
> the code to behave correctly", I think it's best to use memzero_explicit() to
> make the intent clear, even if it seems that memset() is sufficient.  Also keep
> in mind that support for compiling the kernel with LTO (link-time optimization)
> is being worked on (and some people already do it), which results in more code
> being optimized out.

The rule up until now has been that we only use memzero_explicit for
stack variables.  At this point please don't convert anything else
as it will cause too much churn.

If LTO did arrive we should do a global conversion.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt