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From:   Stephan Mueller <smueller@chronox.de>
To:     herbert@gondor.apana.org.au, davem@davemloft.net, trix@redhat.com
Cc:     linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        Tom Rix <trix@redhat.com>
Subject: Re: [PATCH] crypto: drbg: check blocklen is non zero
Date:   Sun, 02 Aug 2020 20:29:05 +0200
Message-ID: <9904643.2WqB4rESCP@tauon.chronox.de>
In-Reply-To: <20200802171247.16558-1-trix@redhat.com>
References: <20200802171247.16558-1-trix@redhat.com>
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Am Sonntag, 2. August 2020, 19:12:47 CEST schrieb trix@redhat.com:

Hi Tom,

> From: Tom Rix <trix@redhat.com>
> 
> Clang static analysis reports this error
> 
> crypto/drbg.c:441:40: warning: Division by zero
>         padlen = (inputlen + sizeof(L_N) + 1) % (drbg_blocklen(drbg));
>                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
> 
> When drbg_bocklen fails it returns 0.
> 
> 	if (drbg && drbg->core)
> 		return drbg->core->blocklen_bytes;
> 	return 0;
> 
> In many places in drbg_ctr_df drbg_bocklen is assumed to be non zero.
> So turn the assumption into a check.
> 
> Fixes: 541af946fe13 ("crypto: drbg - SP800-90A Deterministic Random Bit
> Generator")
> 
> Signed-off-by: Tom Rix <trix@redhat.com>

Thank you.

Reviewed-by: Stephan Mueller <smueller@chronox.de>

Ciao
Stephan