linux-ext4 - Re: [f2fs-dev] [PATCH] fscrypt: use 32 bytes of encrypted filename

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Date:   Fri, 21 Apr 2017 12:26:25 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     Gwendal Grignou <gwendal@...omium.org>, hashimoto@...omium.org,
        ebiggers@...gle.com, linux-f2fs-devel@...ts.sourceforge.net,
        linux-fscrypt@...r.kernel.org, linux-mtd@...ts.infradead.org,
        tytso@....edu, linux-ext4@...r.kernel.org, kinaba@...omium.org
Subject: Re: [f2fs-dev] [PATCH] fscrypt: use 32 bytes of encrypted filename

Hi Jaegeuk,

On Fri, Apr 21, 2017 at 10:35:03AM -0700, Jaegeuk Kim wrote:
> 
> > In any case, I guess that unless there are other ideas we can do these patches:
> > 
> > 1.) f2fs patch to start checking the name, as above
> > 2.) patch to start encoding last 32 bytes of the name (or second-to-last CTS
> >     block, I haven't decided yet) rather than last 16 bytes, changing
> >     fs/crypto/, fs/ext4/, and fs/f2fs/
> > 3.) cleanup patches to introduce helper function and switch ext4 and f2fs to it
> 
> IMO, it'd better to do 3.) followed by 2.), since 2.) already needs to change
> fs/crypto which does not give much backporting effort.
> 

That would be ideal, but unfortunately the main users of filesystem encryption
are using old kernel versions which don't have fs/crypto/, usually 4.4 at
latest.  So it would be nice for it to be easier to backport the "use different
bytes from the encrypted filename" change to 4.4-stable, as I've been doing for
some of the other filesystem encryption fixes.  And people do need it, it seems,
as it causes real problems like undeletable files; Gwendal is even already
trying to merge a fix into some Chrome OS kernel.

> 
> I found one issue in my patch and modified it in f2fs tree [1]. Given next merge
> window probable starting next week, let me upstream this modified one first
> through f2fs. Then, you can see it in 4.12-rc1 two weeks later, so fscrypt
> patches can be easily integrated after then. If you have any concern, I'm also
> okay to push this patch through fscrypt. Let me know.
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?h=dev-test&id=1585cfbbb269be6a112e0629a52123c0f9eaf4fa
> 

I think the series through fscrypt makes more sense, though if I don't have it
ready soon please go ahead and take the f2fs portion through the f2fs tree.

Thanks!

- Eric