From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
Jaegeuk Kim <jaegeuk@kernel.org>,
Victor Hsieh <victorhsieh@google.com>,
Chandan Rajendra <chandan@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 01/12] fs-verity: add a documentation file
Date: Tue, 18 Dec 2018 19:16:03 -0500 [thread overview]
Message-ID: <20181219001603.GD25775@mit.edu> (raw)
In-Reply-To: <20181217200039.GD8111@magnolia>
On Mon, Dec 17, 2018 at 12:00:39PM -0800, Darrick J. Wong wrote:
> FWIW, if I were (hypothetically) working on an xfs implementation, I
> likely would have settled on passing a reference to a merkle tree
> through a (fd, length) pair, because that allows us plenty of options
> on the back end:
>
> b) we could remap the tree into a new inode fork for merkle trees, or
> a) remap it as posteof blocks like ext4/f2fs does, or
> c) remap the blocks into the attribute fork as an (unusually large)
> extended attribute value.
Sure, but what would be the benefit of doing different things on the
back end? I think this is a really more of a philophical objection
than anything else. With both fsverity and fscrypt, well over 95% of
the implementation is shared between ext4 and f2fs. And from a
cryptographic design, that's something I consider a feature, not a
bug. Cryptographic code is subtle in very different ways compared to
file system code. So it's a good thing to having it done once and
audited by crypto specialists, as opposed to having each file system
doing it differently / independently.
> If the merkle_fd isn't on the same filesystem as the fd we could at
> least use generic_copy_file_range (i.e. page cache copying) to land the
> merkle tree wherever we want.
>
> Granted, it's not like we can't do any of those three things given the
> current interface. I gather most of the grumbling has to do with
> feeling like we're associating the on-disk format to the ioctl interface
> too closely?
Right, the current interface makes it somewhat more awkward to do
these other things --- but the question is *why* would you want to in
the first place? Why add the extra complexity? I'm a big believer of
the KISS principle, and if there was a reason why a file system would
want to store the Merkle tree somewhere else, we could talk about it,
but I see only downside, and no upside.
- Ted
next prev parent reply other threads:[~2018-12-19 0:16 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 22:52 [PATCH v2 00/12] fs-verity: read-only file-based authenticity protection Eric Biggers
2018-11-01 22:52 ` [PATCH v2 01/12] fs-verity: add a documentation file Eric Biggers
2018-12-12 9:14 ` Christoph Hellwig
2018-12-12 20:26 ` Eric Biggers
2018-12-13 20:22 ` Christoph Hellwig
2018-12-14 4:48 ` Eric Biggers
2018-12-17 16:49 ` Christoph Hellwig
2018-12-17 18:32 ` Eric Biggers
2018-12-19 7:09 ` Christoph Hellwig
2018-12-17 20:00 ` Darrick J. Wong
2018-12-19 0:16 ` Theodore Y. Ts'o [this message]
2018-12-19 2:19 ` Dave Chinner
2018-12-19 19:30 ` Theodore Y. Ts'o
2018-12-19 21:35 ` Dave Chinner
2018-12-20 22:01 ` Theodore Y. Ts'o
2018-12-21 7:04 ` Christoph Hellwig
2018-12-21 10:06 ` Richard Weinberger
2018-12-21 15:47 ` Theodore Y. Ts'o
2018-12-21 15:53 ` Matthew Wilcox
2018-12-21 16:28 ` Theodore Y. Ts'o
2018-12-21 16:34 ` Matthew Wilcox
2018-12-21 19:13 ` Linus Torvalds
2018-12-22 4:17 ` Theodore Y. Ts'o
2018-12-22 22:47 ` Linus Torvalds
2018-12-23 4:34 ` Theodore Y. Ts'o
2018-12-23 4:10 ` Matthew Wilcox
2018-12-23 4:45 ` Theodore Y. Ts'o
2019-01-04 20:41 ` Daniel Colascione
2018-12-19 7:14 ` Christoph Hellwig
2018-12-19 7:11 ` Christoph Hellwig
[not found] ` <CAHk-=wiB8vGbje+NgNkMZupHsZ_cqg6YEBV+ZXSF4wnywFLRHQ@mail.gmail.com>
2018-12-19 7:19 ` Christoph Hellwig
2018-12-14 5:17 ` Theodore Y. Ts'o
2018-12-14 5:39 ` Eric Biggers
2018-12-17 16:52 ` Christoph Hellwig
2018-12-17 19:15 ` Eric Biggers
2018-12-21 16:11 ` Matthew Wilcox
2018-11-01 22:52 ` [PATCH v2 02/12] fs-verity: add setup code, UAPI, and Kconfig Eric Biggers
2018-11-01 22:52 ` [PATCH v2 03/12] fs-verity: add MAINTAINERS file entry Eric Biggers
2018-11-01 22:52 ` [PATCH v2 04/12] fs-verity: add data verification hooks for ->readpages() Eric Biggers
2018-11-01 22:52 ` [PATCH v2 05/12] fs-verity: implement FS_IOC_ENABLE_VERITY ioctl Eric Biggers
2018-11-01 22:52 ` [PATCH v2 06/12] fs-verity: implement FS_IOC_MEASURE_VERITY ioctl Eric Biggers
2018-11-01 22:52 ` [PATCH v2 07/12] fs-verity: add SHA-512 support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 08/12] fs-verity: add CRC-32C support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 09/12] fs-verity: support builtin file signatures Eric Biggers
2018-11-01 22:52 ` [PATCH v2 10/12] ext4: add basic fs-verity support Eric Biggers
2018-11-02 9:43 ` Chandan Rajendra
2018-11-06 1:25 ` Eric Biggers
2018-11-06 6:52 ` Chandan Rajendra
2018-11-05 21:05 ` Andreas Dilger
2018-11-06 1:11 ` Eric Biggers
2018-11-01 22:52 ` [PATCH v2 11/12] ext4: add fs-verity read support Eric Biggers
2018-11-01 22:52 ` [PATCH v2 12/12] f2fs: fs-verity support Eric Biggers
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