From: Dave Chinner <david@fromorbit.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Jann Horn <jannh@google.com>, Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
linux-fsdevel@vger.kernel.org,
"Eric W. Biederman" <ebiederm@xmission.com>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: don't let getdents return bogus names
Date: Thu, 19 Jul 2018 10:50:00 +1000 [thread overview]
Message-ID: <20180719005000.GE19934@dastard> (raw)
In-Reply-To: <20180716195657.GO30522@ZenIV.linux.org.uk>
On Mon, Jul 16, 2018 at 08:56:57PM +0100, Al Viro wrote:
> On Mon, Jul 16, 2018 at 09:48:43PM +0200, Jann Horn wrote:
> > When you e.g. run `find` on a directory for which getdents returns
> > "filenames" that contain slashes, `find` passes those "filenames" back to
> > the kernel, which then interprets them as paths. That could conceivably
> > cause userspace to do something bad when accessing something like an
> > untrusted USB stick, but I'm not aware of any specific example.
> >
> > Instead of returning bogus filenames to userspace, return -EUCLEAN.
>
> Because there's such a lot of userland code that expect and handles that
> error value...
We've been using EUCLEAN ("structure needs cleaning") for indicating
filesystem corruption errors for many years now. e.g.
fs/ext2/ext2.h:#define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */
fs/ext4/ext4.h:#define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */
fs/hpfs/hpfs_fn.h:#define EFSERROR EUCLEAN
fs/xfs/xfs_linux.h:#define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */
include/linux/jbd2.h:#define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */
There's hundreds of places in the filesystem code that this
specific error is returned to userspace - there's more than 500
individual places this error can be returned from just XFS....
To me it seems like the right error to return if a dirent is
corrupted, because that's exactly what XFS will return if any of the
directory structure around the dirent name itself is corrupt...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2018-07-19 0:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 19:48 [PATCH] fs: don't let getdents return bogus names Jann Horn
2018-07-16 19:56 ` Al Viro
2018-07-16 20:20 ` Jann Horn
2018-07-19 0:50 ` Dave Chinner [this message]
2018-07-29 11:37 ` Pavel Machek
2018-07-16 21:47 ` kbuild test robot
2018-07-16 21:47 ` kbuild test robot
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