Date: Sun, 28 Apr 2013 08:11:22 +0800
From: Herbert Xu <herbert@gondor.hengli.com.au>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>, "David S. Miller" <davem@davemloft.net>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        James Bottomley <James.Bottomley@HansenPartnership.com>,
        Matthew Wilcox <willy@linux.intel.com>,
        Jim Kukunas <james.t.kukunas@linux.intel.com>,
        Keith Busch <keith.busch@intel.com>,
        Erdinc Ozturk <erdinc.ozturk@intel.com>,
        Vinodh Gopal <vinodh.gopal@intel.com>,
        James Guilford <james.guilford@intel.com>,
        Wajdi Feghali <wajdi.k.feghali@intel.com>,
        Jussi Kivilinna <jussi.kivilinna@iki.fi>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-crypto@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: [PATCH v2 1/4] Wrap crc_t10dif function all to use crypto
 transform framework
Message-ID: <20130428001122.GA6973@gondor.apana.org.au>
References: <cover.1366214842.git.tim.c.chen@linux.intel.com>
 <ea4271721b5ca130849b03da4f172f12f66e5628.1366214842.git.tim.c.chen@linux.intel.com>
 <20130425132203.GA29501@gondor.apana.org.au>
 <1366910910.27102.126.camel@schen9-DESK>
 <20130426125224.GA4855@gondor.apana.org.au>
 <1366994657.27102.129.camel@schen9-DESK>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1366994657.27102.129.camel@schen9-DESK>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1285
Lines: 38

On Fri, Apr 26, 2013 at 09:44:17AM -0700, Tim Chen wrote:
>
> +	old_tfm = crct10dif_tfm;
> +	crc_t10dif_newalg = true;
> +	/* make sure new alg flag is turned on before starting to switch tfm */
> +	mb();
> +
> +	new_tfm = crypto_alloc_shash("crct10dif", 0, 0);
> +	if (IS_ERR(new_tfm))
> +		goto done;
> +
> +	if (old_tfm)
> +		if (crypto_tfm_alg_priority(&old_tfm->base) >=
> +		    crypto_tfm_alg_priority(&new_tfm->base)) {
> +			crypto_free_shash(new_tfm);
> +			goto done;
> +		}
> +	crct10dif_tfm = new_tfm;
> +	/* make sure update to tfm pointer is completed */
> +	mb();
> +	crypto_free_shash(old_tfm);

This is not safe at all.  You'd need to use something like RCU.

However, I think this is an overkill.  Initialising it once should
be enough.  If someone really wanted to change things at run-time,
they could always build this as a module and unload/reload it.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/