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Date:   Sun, 18 Aug 2019 09:16:38 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     "Theodore Y. Ts'o" <tytso@mit.edu>,
        Richard Weinberger <richard@nod.at>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Gao Xiang <hsiangkao@aol.com>, Jan Kara <jack@suse.cz>,
        Chao Yu <yuchao0@huawei.com>,
        Dave Chinner <david@fromorbit.com>,
        David Sterba <dsterba@suse.cz>, Miao Xie <miaoxie@huawei.com>,
        devel <devel@driverdev.osuosl.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Darrick <darrick.wong@oracle.com>,
        Amir Goldstein <amir73il@gmail.com>,
        linux-erofs <linux-erofs@lists.ozlabs.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Li Guifu <bluce.liguifu@huawei.com>,
        Fang Wei <fangwei1@huawei.com>, Pavel Machek <pavel@denx.de>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] erofs: move erofs out of staging
Message-ID: <20190818161638.GE1118@sol.localdomain>
Mail-Followup-To: Christoph Hellwig <hch@infradead.org>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        Richard Weinberger <richard@nod.at>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Gao Xiang <hsiangkao@aol.com>, Jan Kara <jack@suse.cz>,
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        David Sterba <dsterba@suse.cz>, Miao Xie <miaoxie@huawei.com>,
        devel <devel@driverdev.osuosl.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Darrick <darrick.wong@oracle.com>,
        Amir Goldstein <amir73il@gmail.com>,
        linux-erofs <linux-erofs@lists.ozlabs.org>,
        Al Viro <viro@zeniv.linux.org.uk>, Jaegeuk Kim <jaegeuk@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Li Guifu <bluce.liguifu@huawei.com>, Fang Wei <fangwei1@huawei.com>,
        Pavel Machek <pavel@denx.de>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        torvalds <torvalds@linux-foundation.org>
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On Sun, Aug 18, 2019 at 08:58:12AM -0700, Christoph Hellwig wrote:
> On Sun, Aug 18, 2019 at 11:11:54AM -0400, Theodore Y. Ts'o wrote:
> > Note that of the mainstream file systems, ext4 and xfs don't guarantee
> > that it's safe to blindly take maliciously provided file systems, such
> > as those provided by a untrusted container, and mount it on a file
> > system without problems.  As I recall, one of the XFS developers
> > described file system fuzzing reports as a denial of service attack on
> > the developers.
> 
> I think this greatly misrepresents the general attitute of the XFS
> developers.  We take sanity checks for the modern v5 on disk format
> very series, and put a lot of effort into handling corrupted file
> systems as good as possible, although there are of course no guaranteeѕ.
> 
> The quote that you've taken out of context is for the legacy v4 format
> that has no checksums and other integrity features.

Ted's observation was about maliciously-crafted filesystems, though, so
integrity-only features such as metadata checksums are irrelevant.  Also the
filesystem version is irrelevant; anything accepted by the kernel code (even if
it's legacy/deprecated) is open attack surface.

I personally consider it *mandatory* that we deal with this stuff.  But I can
understand that we don't do a good job at it, so we shouldn't hold a new
filesystem to an unfairly high standard relative to other filesystems...

- Eric