linux-kernel - Re: [PATCH] crypto: xts_crypt() return if walk.nbytes is 0

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Date:   Fri, 20 Aug 2021 16:31:11 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
Cc:     davem@...emloft.net, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com, ardb@...nel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+20191dc583eff8602d2d@...kaller.appspotmail.com
Subject: Re: [PATCH] crypto: xts_crypt() return if walk.nbytes is 0

On Mon, Aug 09, 2021 at 07:40:27PM +0530, Shreyansh Chouhan wrote:
> xts_crypt() code doesn't call kernel_fpu_end() after calling
> kernel_fpu_begin() if walk.nbytes is 0. The correct behavior should be
> not calling kernel_fpu_begin() if walk.nbytes is 0.
> 
> Reported-by: syzbot+20191dc583eff8602d2d@...kaller.appspotmail.com
> Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
> ---
>  arch/x86/crypto/aesni-intel_glue.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
> index 388643ca2177..ec6eac57c493 100644
> --- a/arch/x86/crypto/aesni-intel_glue.c
> +++ b/arch/x86/crypto/aesni-intel_glue.c
> @@ -849,7 +849,7 @@ static int xts_crypt(struct skcipher_request *req, bool encrypt)
>  		return -EINVAL;
>  
>  	err = skcipher_walk_virt(&walk, req, false);
> -	if (err)
> +	if (err || !walk.nbytes)
>  		return err;

The err check is now redundant because when there is an error
nbytes is always zero.

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