linux-ext4 - Re: [PATCH v10 02/12] block: Keyslot Manager for Inline Encryption

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Message-ID: <20200428051956.GB24105@infradead.org>
Date:   Mon, 27 Apr 2020 22:19:56 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Satya Tangirala <satyat@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-block@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-ext4@...r.kernel.org,
        Barani Muthukumaran <bmuthuku@....qualcomm.com>,
        Kuohong Wang <kuohong.wang@...iatek.com>,
        Kim Boojin <boojin.kim@...sung.com>
Subject: Re: [PATCH v10 02/12] block: Keyslot Manager for Inline Encryption

On Mon, Apr 27, 2020 at 07:57:08PM -0700, Eric Biggers wrote:
> Or maybe 'struct blk_ksm_keyslot' should contain a pointer to the
> 'struct blk_crypto_key' rather than a copy of it?  If we did that, then:
> 
> - Each duplicate blk_crypto_key would use its own keyslot and not interfere with
>   any others.
> 
> - blk_crypto_evict_key() would be *required* to be called.
> 
> - It would be a kernel bug if blk_crypto_evict_key() were called with any
>   pending I/O, so WARN_ON_ONCE() would be the right thing to do.
> 
> - The hash function used to find a key's keyslot would be
>   hash_ptr(blk_crypto_key, ksm->log_slot_hashtable_size) instead of
>   SipHash(key=perboot_key, data=raw_key).
>   
> I might be forgetting something; was there a reason we didn't do that?
> It wouldn't be as robust against users forgetting to call
> blk_crypto_evict_key(), but that would be a bug anyway.

The above sounds pretty sensible to me (but I'm everything but an expert
in the area).