linux-kernel - Re: [PATCH 1/3] dm integrity: do not filter algos with CRYPTO_ALG_ALLOCATES

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Date:   Wed, 5 Jul 2023 13:12:05 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Giovanni Cabiddu <giovanni.cabiddu@...el.com>
Cc:     herbert@...dor.apana.org.au, agk@...hat.com, snitzer@...nel.org,
        linux-crypto@...r.kernel.org, dm-devel@...hat.com,
        linux-kernel@...r.kernel.org, qat-linux@...el.com,
        heinzm@...hat.com, meenakshi.aggarwal@....com,
        horia.geanta@....com, V.Sethi@....com, pankaj.gupta@....com,
        gaurav.jain@....com, davem@...emloft.net, iuliana.prodan@....com,
        Fiona Trahe <fiona.trahe@...el.com>
Subject: Re: [PATCH 1/3] dm integrity: do not filter algos with
 CRYPTO_ALG_ALLOCATES_MEMORY

On Wed, Jul 05, 2023 at 05:40:07PM +0100, Giovanni Cabiddu wrote:
> The flag CRYPTO_ALG_ALLOCATES_MEMORY indicates that an algorithm might
> allocate memory in the datapath and therefore sleep.
> Dm-integrity is filtering out implementations of skcipher algorithms
> that have this flag set. However, in the same function it does
> allocations with GFP_KERNEL.

Which function is the above referring to?  The actual encryption/decryption
happens in crypt_journal(), and I don't see any memory allocations there.

> As dm-integrity is re-entrant and capable of handling sleeps that could
> occur during allocations with GFP_KERNEL, then it is also capable of
> using skcipher algorithm implementations that have
> CRYPTO_ALG_ALLOCATES_MEMORY set.
> 
> Remove the filtering of skcipher implementations with the flag
> CRYPTO_ALG_ALLOCATES_MEMORY set.

What about the use of CRYPTO_ALG_ALLOCATES_MEMORY in get_mac()?

> 
> Suggested-by: Herbert Xu <herbert@...dor.apana.org.au>
> Link: https://lore.kernel.org/linux-crypto/ZILvtASXQKLG43y9@gondor.apana.org.au/
> Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@...el.com>
> Reviewed-by: Fiona Trahe <fiona.trahe@...el.com>

This needs:

    Fixes: a7a10bce8a04 ("dm integrity: don't use drivers that have CRYPTO_ALG_ALLOCATES_MEMORY")
    Cc: stable@...r.kernel.org

But, are you 100% sure the explanation in commit a7a10bce8a04 was incorrect?

- Eric