linux-kernel - Re: [PATCH 16/18] crypto: talitos - do hw_context DMA mapping outside the requests

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Message-ID: <VI1PR0402MB334299B37F17771BFA9AFDDA98C80@VI1PR0402MB3342.eurprd04.prod.outlook.com>
Date:   Mon, 19 Feb 2018 13:16:30 +0000
From:   Horia Geant <horia.geanta@....com>
To:     Christophe LEROY <christophe.leroy@....fr>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
CC:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 16/18] crypto: talitos - do hw_context DMA mapping outside
 the requests

On 2/19/2018 11:14 AM, Christophe LEROY wrote:
> Le 19/02/2018 à 09:30, Horia Geantă a écrit :
>> On 2/19/2018 9:58 AM, Christophe LEROY wrote:
>>> Le 18/02/2018 à 18:14, Horia Geantă a écrit :
>>>> There is no ahash_exit() callback mirroring ahash_init().
>>>>
>>>> The clean-up of request ctx should be done in the last states of the hash flows
>>>> described here:
>>>> https://www.kernel.org/doc/html/latest/crypto/devel-algos.html#cipher-definition-with-struct-shash-alg-and-ahash-alg
>>>> for e.g. in the final() callback.
>>>
>>> Unfortunatly it seems that we can't rely on those finalising functions
>>> being called all the time.
>>> If you look into test_ahash_jiffies() for instance, in case of error the
>>> call of crypto_hash_final() is skipped.
>>
>> If test_ahash_jiffies() errors before calling crypto_ahash_final(req), this
>> means a previous callback failed.
>> Accordingly, DMA unmapping should be performed also on the corresponding errors
>> paths in the driver.
>>
> 
> And what about ALGIF path from user space ?
> What if the user never calls the last sendmsg() which will call 
> hash_finup() ?
> 
User is expected to follow the rules of the crypto API.
Of course, kernel won't (or at least shouldn't) crash in case of misuse.
However, in these cases some resources might not be freed - it's unavoidable.

Horia