linux-kernel - Re: [f2fs-dev] [PATCH AUTOSEL 5.10 10/31] f2fs: Handle casefolding with Encryption

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Message-ID: <X+zAlEu+0JSvXaMu@sol.localdomain>
Date:   Wed, 30 Dec 2020 10:01:56 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        Daniel Rosenberg <drosen@...gle.com>
Subject: Re: [f2fs-dev] [PATCH AUTOSEL 5.10 10/31] f2fs: Handle casefolding
 with Encryption

On Wed, Dec 30, 2020 at 08:02:52AM -0500, Sasha Levin wrote:
> From: Daniel Rosenberg <drosen@...gle.com>
> 
> [ Upstream commit 7ad08a58bf67594057362e45cbddd3e27e53e557 ]
> 
> Expand f2fs's casefolding support to include encrypted directories.  To
> index casefolded+encrypted directories, we use the SipHash of the
> casefolded name, keyed by a key derived from the directory's fscrypt
> master key.  This ensures that the dirhash doesn't leak information
> about the plaintext filenames.
> 
> Encryption keys are unavailable during roll-forward recovery, so we
> can't compute the dirhash when recovering a new dentry in an encrypted +
> casefolded directory.  To avoid having to force a checkpoint when a new
> file is fsync'ed, store the dirhash on-disk appended to i_name.
> 
> This patch incorporates work by Eric Biggers <ebiggers@...gle.com>
> and Jaegeuk Kim <jaegeuk@...nel.org>.
> 
> Co-developed-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Daniel Rosenberg <drosen@...gle.com>
> Reviewed-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

Please don't backport this to the LTS kernels.  This is a new feature, not a
fix, and you missed prerequisite patches...

- Eric