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

From: Christoph Hellwig <hch@infradead.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Satya Tangirala <satyat@google.com>,
	Christoph Hellwig <hch@infradead.org>,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-ext4@vger.kernel.org,
	Barani Muthukumaran <bmuthuku@qti.qualcomm.com>,
	Kuohong Wang <kuohong.wang@mediatek.com>,
	Kim Boojin <boojin.kim@samsung.com>
Subject: Re: [PATCH v10 02/12] block: Keyslot Manager for Inline Encryption
Date: Mon, 27 Apr 2020 22:19:56 -0700	[thread overview]
Message-ID: <20200428051956.GB24105@infradead.org> (raw)
In-Reply-To: <20200428025708.GB251491@gmail.com>

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).