linux-kernel - Re: [PATCH 0/7] ensure bios aren't split in middle of crypto data unit

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Message-ID: <20210121171129.GA4122715@infradead.org>
Date:   Thu, 21 Jan 2021 17:11:29 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Satya Tangirala <satyat@...gle.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 0/7] ensure bios aren't split in middle of crypto data
 unit

On Thu, Jan 14, 2021 at 03:47:16PM +0000, Satya Tangirala wrote:
> When a bio has an encryption context, its size must be aligned to its
> crypto data unit size. A bio must not be split in the middle of a data
> unit. Currently, bios are split at logical block boundaries, but a crypto
> data unit size might be larger than the logical block size - e.g. a machine
> could be using fscrypt (which uses 4K crypto data units) with an eMMC block
> device with inline encryption hardware that has a logical block size of
> 512 bytes. So we need to support cases where the data unit size is larger
> than the logical block size.

I think this model is rather broken.  Instead of creating an -EIO path
we can't handle anywhere make sure that the size limits exposed by the
driver that wants to split always align to the crypto data units to
avoid this issue to start with.