Messages in this thread |  | | From | Stephan Mueller <> | Subject | Re: [PATCH v3] crypto: remove instance when test failed | Date | Thu, 09 Apr 2015 11:22:19 +0200 |
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Am Donnerstag, 9. April 2015, 15:41:41 schrieb Herbert Xu:
Hi Herbert,
>On Thu, Apr 09, 2015 at 09:36:03AM +0200, Stephan Mueller wrote: >> diff --git a/crypto/algapi.c b/crypto/algapi.c >> index f1d0307..cfca1de 100644 >> --- a/crypto/algapi.c >> +++ b/crypto/algapi.c >> @@ -533,6 +533,13 @@ int crypto_register_instance(struct crypto_template >> *tmpl,> >> if (IS_ERR(larval)) >> >> goto unlock; >> >> + err = -EAGAIN; >> + if (unlikely(!crypto_mod_get(&inst->alg))) { >> + up_write(&crypto_alg_sem); >> + crypto_unregister_instance(inst); >> + goto err; >> + } > >Just grab the reference count as soon as you enter the function >and then you can unconditionally drop the reference count at the >end. If you fail to grab it then just return an error and the >caller will free it for you.
I tested it and this approach does not work.
If I see that right, the reason for that is the following: The suggestion is to grab the ref count at the start of the function followed by a __crypto_register_alg. __crypto_register_alg however sets the refcount to 1 unconditionally. That means that the final put of the alg will most likely set the refcount to 0 that causes an issue with all other operations (at least I cannot allocate HMAC or CMAC any more -- the ones I currently test).
So, the grabing of the alg must happen after the invocation of __crypto_register_alg. > >Cheers,
Ciao Stephan
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