linux-ext4 - Re: [PATCH v3 0/3] ext4 crypto: back up encrypted files

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20151218004935.GA17115@thunk.org>
Date:	Thu, 17 Dec 2015 19:49:35 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	mhalcrow@...gle.com
Subject: Re: [PATCH v3 0/3] ext4 crypto: back up encrypted files

On Wed, Dec 16, 2015 at 04:10:10PM +0100, Jan Kara wrote:
> 
> Umm, I don't quite follow. O_DIRECT reads will actually read final file
> block in full even if i_size is somewhere in the middle of it. We then
> report only data upto i_size as transferred but that's not really
> important for you.

I had tried this approach first but it appeared that the data was
getting zero'ed between i_size and the end of the block.  It turns out
it was a bug in my test program, sigh.

I agree about the locking issues.  It isn't so much of an issue since
without the encryption key, you can't modify the file, so this
prevents most of the nasty races.  Of course, it could be the case
that user A (say, root) doesn't have access to the key, but user B
(say the user account) does have access.  So dropping the shadow inode
is the better way to go.

Thanks!!

						- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html