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From:   Gilad Ben-Yossef <gilad@benyossef.com>
Date:   Thu, 17 Oct 2019 16:45:06 +0300
Message-ID: <CAOtvUMeX1F5+g-jg2vUWaTQX8KHdmtAcb2-r4oVaUwfFYJbmsg@mail.gmail.com>
Subject: Re: [PATCH] crypto: fix comparison of unsigned expression warnings
To:     Tian Tao <tiantao6@huawei.com>
Cc:     Herbert Xu <herbert@gondor.apana.org.au>,
        David Miller <davem@davemloft.net>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        linuxarm@huawei.com
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On Mon, Sep 30, 2019 at 11:52 AM Tian Tao <tiantao6@huawei.com> wrote:
>
> This patch fixes the following warnings:
> drivers/crypto/ccree/cc_aead.c:630:5-12: WARNING: Unsigned expression
> compared with zero: seq_len > 0

Thank you very much for the patch. Please accept my apologies that it
took me some time to respond.

I'm sorry, but I don't think this is the right solution here:

seq_len here can never get a negative value so the warning is a false one.

Having said that, I suspect it would be better code to:
1. change hmac_setkey() return type to unsigned int as well, as it
doesn't ever return a negative number.
2. change the predicate in the if statement the warning mentions to
seq_len !=3D 0.

That would be a clearer code and possibly will also silence the false warni=
ng

So NACK for this one but I would accept a patch doing he above if you send =
one.

Thanks again for taking the time to do this.

Gilad

>
> Signed-off-by: Tian Tao <tiantao6@huawei.com>
> ---
>  drivers/crypto/ccree/cc_aead.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/crypto/ccree/cc_aead.c b/drivers/crypto/ccree/cc_aea=
d.c
> index d3e8faa..b19291d 100644
> --- a/drivers/crypto/ccree/cc_aead.c
> +++ b/drivers/crypto/ccree/cc_aead.c
> @@ -546,7 +546,7 @@ static int cc_aead_setkey(struct crypto_aead *tfm, co=
nst u8 *key,
>         struct cc_aead_ctx *ctx =3D crypto_aead_ctx(tfm);
>         struct cc_crypto_req cc_req =3D {};
>         struct cc_hw_desc desc[MAX_AEAD_SETKEY_SEQ];
> -       unsigned int seq_len =3D 0;
> +       int seq_len =3D 0;
>         struct device *dev =3D drvdata_to_dev(ctx->drvdata);
>         const u8 *enckey, *authkey;
>         int rc;
> --
> 2.7.4
>


--=20
Gilad Ben-Yossef
Chief Coffee Drinker

values of =CE=B2 will give rise to dom!