linux-kernel - Re: Bug report: unaligned access with ext4 encryption

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Message-ID: <17391.1546622882@warthog.procyon.org.uk>
Date:   Fri, 04 Jan 2019 17:28:02 +0000
From:   David Howells <dhowells@...hat.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     dhowells@...hat.com, Aaro Koskinen <aaro.koskinen@....fi>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        linux-fscrypt@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: Bug report: unaligned access with ext4 encryption

Eric Biggers <ebiggers@...nel.org> wrote:

> Hi Aaro, thanks for the bug report!  I think you're on the right track; it makes
> much more sense to have the keyrings subsystem store the payload with better
> alignment, than to work around the 2-byte alignment in fscrypt.
> 
> But how about '__aligned(__alignof__(u64))' instead?  4 bytes may not be enough.
> 
> David, what do you think?

Does that even work?

Might be better to just insert 6 bytes of padding with a comment, but yes I
agree that it's probably better to align it to at least machine word size.

David