linux-kernel - Re: [PATCH RFC 1/3] crypto: Prevent to register duplicate cra_driver

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Date:   Thu, 21 Dec 2017 21:05:20 +0100
From:   LABBE Corentin <clabbe@...libre.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     davem@...emloft.net, nhorman@...driver.com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/3] crypto: Prevent to register duplicate
 cra_driver_name

On Thu, Dec 21, 2017 at 01:35:27PM +0100, LABBE Corentin wrote:
> On Thu, Dec 21, 2017 at 05:35:22PM +1100, Herbert Xu wrote:
> > On Wed, Dec 20, 2017 at 08:09:25PM +0000, Corentin Labbe wrote:
> > > Each crypto algorithm "cra_name" can have multiple implementation called
> > > "cra_driver_name".
> > > If two different implementation have the same cra_driver_name, nothing
> > > can easily differentiate them.
> > > Furthermore the mechanism for getting a crypto algorithm with its
> > > implementation name (crypto_alg_match() in crypto/crypto_user.c) will
> > > get only the first one found.
> > > 
> > > So this patch prevent the registration of two implementation with the
> > > same cra_driver_name.
> > > 
> > > Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> > 
> > No this is intentional.  The idea is that you can hot-replace
> > an implementation by registering a new version of it while the
> > old one is still in use.  The new one will be used for all new
> > allocations.
> > 
> 
> But the new implementation is different from the first so should have a new name.
> The only case I found is ctr-aes-ce, and both are different (use/dontuse simd) so qualifying for different name.
> 
> Anyway, any advice on how to populate properly /sys/crypto with unique name ?
> I have two idea:
> - A number which increment after each register
> - cra_driver_name-priority
> 
> Or does I use /sys/crypto/cra_driver_name/priority ? (which need to use some usage count on cra_driver_name node)

I just see that kobject already have reference counting so this solution is the better.

Regards