linux-kernel - Re: [PATCH v5 00/11] blksnap - block devices snapshots module

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Message-ID: <ZIgDlA/nMQIMqeLU@infradead.org>
Date:   Mon, 12 Jun 2023 22:50:12 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Sergei Shtepa <sergei.shtepa@...am.com>, axboe@...nel.dk,
        hch@...radead.org, corbet@....net, snitzer@...nel.org,
        viro@...iv.linux.org.uk, brauner@...nel.org, dchinner@...hat.com,
        willy@...radead.org, dlemoal@...nel.org, linux@...ssschuh.net,
        jack@...e.cz, ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v5 00/11] blksnap - block devices snapshots module

On Mon, Jun 12, 2023 at 09:19:11AM -0700, Eric Biggers wrote:
> On Mon, Jun 12, 2023 at 03:52:17PM +0200, Sergei Shtepa wrote:
> > Hi all.
> > 
> > I am happy to offer a improved version of the Block Devices Snapshots
> > Module. It allows to create non-persistent snapshots of any block devices.
> > The main purpose of such snapshots is to provide backups of block devices.
> > See more in Documentation/block/blksnap.rst.
> 
> How does blksnap interact with blk-crypto?
> 
> I.e., what happens if a bio with a ->bi_crypt_context set is submitted to a
> block device that has blksnap active?
> 
> If you are unfamiliar with blk-crypto, please read
> Documentation/block/inline-encryption.rst
> 
> It looks like blksnap hooks into the block layer directly, via the new
> "blkfilter" mechanism.  I'm concerned that it might ignore ->bi_crypt_context
> and write data to the disk in plaintext, when it is supposed to be encrypted.

Yeah.  Same for integrity.  I guess for now the best would be to
not allow attaching a filter to block devices that have encryption or
integrity enabled and then look into that as a separate project fully
reviewed by the respective experts.