From: Gao Xiang <gaoxiang25@huawei.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
Goldwyn Rodrigues <RGoldwyn@suse.com>, "hch@lst.de" <hch@lst.de>,
"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
"ruansy.fnst@cn.fujitsu.com" <ruansy.fnst@cn.fujitsu.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
<linux-erofs@lists.ozlabs.org>, <miaoxie@huawei.com>
Subject: Re: [PATCH 10/13] iomap: use a function pointer for dio submits
Date: Thu, 8 Aug 2019 21:11:39 +0800 [thread overview]
Message-ID: <20190808131139.GH28630@138> (raw)
In-Reply-To: <20190808112139.GG28630@138>
On Thu, Aug 08, 2019 at 07:21:39PM +0800, Gao Xiang wrote:
> On Thu, Aug 08, 2019 at 05:29:47PM +0800, Gao Xiang wrote:
> > On Thu, Aug 08, 2019 at 06:16:47PM +1000, Dave Chinner wrote:
> > > On Wed, Aug 07, 2019 at 10:49:36PM -0700, Eric Biggers wrote:
> > > > FWIW, the only order that actually makes sense is decrypt->decompress->verity.
> > >
> > > *nod*
> > >
> > > Especially once we get the inline encryption support for fscrypt so
> > > the storage layer can offload the encrypt/decrypt to hardware via
> > > the bio containing plaintext. That pretty much forces fscrypt to be
> > > the lowest layer of the filesystem transformation stack. This
> > > hardware offload capability also places lots of limits on what you
> > > can do with block-based verity layers below the filesystem. e.g.
> > > using dm-verity when you don't know if there's hardware encryption
> > > below or software encryption on top becomes problematic...
>
> ...and I'm not talking of fs-verity, I personally think fs-verity
> is great. I am only talking about a generic stuff.
>
> In order to know which level becomes problematic, there even could
> be another choice "decrypt->verity1->decompress->verity2" for such
> requirement (assuming verity1/2 themselves are absolutely bug-free),
> verity1 can be a strong merkle tree and verity2 is a weak form (just
> like a simple Adler-32/crc32 in compressed block), thus we can locate
> whether it's a decrypt or decompress bug.
>
> Many compression algorithm containers already have such a weak
> form such as gzip algorithm, so there is no need to add such
> an extra step to postprocess.
>
> and I have no idea which (decrypt->verity1->decompress->verity2 or
> decrypt->decompress->verity) is faster since verity2 is rather simple.
> However, if we use the only strong form in the end, there could be
> a lot of extra IO and expensive multiple-level computations if files
> are highly compressible.
>
> On the other hand, such verity2 can be computed offline / avoided
> by fuzzer tools for read-only scenerios (for example, after building
> these images and do a full image verification with the given kernel)
> in order to make sure its stability (In any case, I'm talking about
> how to make those algorithms bug-free).
>
> All I want to say is I think "decrypt->verity->decompress" is
> reasonable as well.
... And another fundamental concern is that if we don't verify earlier
(I mean on-disk data), then untrusted data will be transformed
(decompressed and even decrypted if no inline encryption) with risk,
and it seems _vulnerable_ if such decrypt / decompress algorithms have
_security issues_ (such as Buffer Overflow). It seems that it's less
security than do verity earlier.
Thanks,
Gao Xiang
>
> Thanks,
> Gao Xiang
>
> >
> > Add a word, I was just talking benefits between "decrypt->decompress->
> > verity" and "decrypt->verity->decompress", I think both forms are
> > compatible with inline en/decryption. I don't care which level
> > "decrypt" is at... But maybe some user cares. Am I missing something?
> >
> > Thanks,
> > Gao Xiang
> >
next prev parent reply other threads:[~2019-08-08 12:54 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 22:00 [PATCH v2 0/13] Btrfs iomap Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 01/13] iomap: Use a IOMAP_COW/srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-08-03 0:39 ` Darrick J. Wong
2019-08-05 0:06 ` Dave Chinner
2019-08-02 22:00 ` [PATCH 02/13] iomap: Read page from srcmap for IOMAP_COW Goldwyn Rodrigues
2019-08-03 0:23 ` Darrick J. Wong
2019-08-04 23:52 ` Dave Chinner
2019-08-02 22:00 ` [PATCH 03/13] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 04/13] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-08-05 0:11 ` Dave Chinner
2019-08-22 15:05 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 05/13] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-08-05 0:13 ` Dave Chinner
2019-08-22 15:01 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 06/13] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 07/13] btrfs: basic direct read operation Goldwyn Rodrigues
2019-08-12 12:32 ` RITESH HARJANI
2019-08-22 15:00 ` Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 08/13] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 09/13] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 10/13] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-08-03 0:21 ` Darrick J. Wong
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-04 23:43 ` Dave Chinner
2019-08-05 16:08 ` Goldwyn Rodrigues
2019-08-05 21:54 ` Dave Chinner
2019-08-08 4:26 ` Gao Xiang
2019-08-08 4:52 ` Gao Xiang
2019-08-08 5:49 ` Eric Biggers
2019-08-08 6:28 ` Gao Xiang
2019-08-08 8:16 ` Dave Chinner
2019-08-08 8:57 ` Gao Xiang
2019-08-08 9:29 ` Gao Xiang
2019-08-08 11:21 ` Gao Xiang
2019-08-08 13:11 ` Gao Xiang [this message]
2019-08-09 20:45 ` Matthew Wilcox
2019-08-09 23:45 ` Gao Xiang
2019-08-10 0:31 ` Eric Biggers
2019-08-10 0:50 ` Eric Biggers
2019-08-10 1:34 ` Gao Xiang
2019-08-10 1:13 ` Gao Xiang
2019-08-10 0:17 ` Eric Biggers
2019-08-02 22:00 ` [PATCH 11/13] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 12/13] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-08-02 22:00 ` [PATCH 13/13] btrfs: update inode size during bio completion Goldwyn Rodrigues
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