linux-kernel - Re: [PATCH 4.19 012/168] crypto: ccree

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Message-ID: <20200818092231.GA10974@amd>
Date:   Tue, 18 Aug 2020 11:22:31 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        Markus Elfring <Markus.Elfring@....de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 012/168] crypto: ccree - fix resource leak on error
 path

Hi!

> Fix a small resource leak on the error path of cipher processing.

I believe this one is wrong.

> @@ -149,10 +148,19 @@ static int cc_cipher_init(struct crypto_tfm *tfm)
>  	ctx_p->flow_mode = cc_alg->flow_mode;
>  	ctx_p->drvdata = cc_alg->drvdata;
>  
> +	if (ctx_p->cipher_mode == DRV_CIPHER_ESSIV) {
> +		/* Alloc hash tfm for essiv */
> +		ctx_p->shash_tfm = crypto_alloc_shash("sha256-generic", 0, 0);
> +		if (IS_ERR(ctx_p->shash_tfm)) {
> +			dev_err(dev, "Error allocating hash tfm for ESSIV.\n");
> +			return PTR_ERR(ctx_p->shash_tfm);
> +		}
> +	}

shash_tfm() is only allocated conditionally.

> +free_key:
> +	kfree(ctx_p->user.key);
> +free_shash:
> +	crypto_free_shash(ctx_p->shash_tfm);

But it is freed unconditionally, and free_shash() is not robust
against NULL pointer due to undefined behaviour in crypto_shash_tfm.

Additionally, it would be cleaner to set ctx_p->shash_tfm to NULL in
this path.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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