Re: [PATCH 5.10 CANDIDATE 11/11] xfs: use setattr_copy to set vfs inode attributes

Amir Goldstein
2022-06-22T18:37:08Z

On Wed, Jun 22, 2022 at 7:41 PM Darrick J. Wong <djwong@kernel.org> wrote:
>
> On Fri, Jun 17, 2022 at 01:06:41PM +0300, Amir Goldstein wrote:
> > From: "Darrick J. Wong" <djwong@kernel.org>
> >
> > commit e014f37db1a2d109afa750042ac4d69cf3e3d88e upstream.
> >
> > [remove userns argument of setattr_copy() for backport]
> >
> > Filipe Manana pointed out that XFS' behavior w.r.t. setuid/setgid
> > revocation isn't consistent with btrfs[1] or ext4. Those two
> > filesystems use the VFS function setattr_copy to convey certain
> > attributes from struct iattr into the VFS inode structure.
> >
> > Andrey Zhadchenko reported[2] that XFS uses the wrong user namespace to
> > decide if it should clear setgid and setuid on a file attribute update.
> > This is a second symptom of the problem that Filipe noticed.
> >
> > XFS, on the other hand, open-codes setattr_copy in xfs_setattr_mode,
> > xfs_setattr_nonsize, and xfs_setattr_time. Regrettably, setattr_copy is
> > /not/ a simple copy function; it contains additional logic to clear the
> > setgid bit when setting the mode, and XFS' version no longer matches.
> >
> > The VFS implements its own setuid/setgid stripping logic, which
> > establishes consistent behavior. It's a tad unfortunate that it's
> > scattered across notify_change, should_remove_suid, and setattr_copy but
> > XFS should really follow the Linux VFS. Adapt XFS to use the VFS
> > functions and get rid of the old functions.
> >
> > [1] https://lore.kernel.org/fstests/CAL3q7H47iNQ=Wmk83WcGB-KBJVOEtR9+qGczzCeXJ9Y2KCV25Q@mail.gmail.com/
> > [2] https://lore.kernel.org/linux-xfs/20220221182218.748084-1-andrey.zhadchenko@virtuozzo.com/
> >
> > Fixes: 7fa294c8991c ("userns: Allow chown and setgid preservation")
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > Reviewed-by: Dave Chinner <dchinner@redhat.com>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > Reviewed-by: Christian Brauner <brauner@kernel.org>
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>
> Same question as I posted to Leah's series -- have all the necessary VFS
> fixes and whatnot been backported to 5.10? Such that all the new sgid
> inheritance tests actually pass with this patch applied? :)

The only patch I backorted to 5.10 is:
xfs: fix up non-directory creation in SGID directories

I will check which SGID tests ran on my series.

Personally, I would rather defer THIS patch to a later post to stable
(Leah's patch as well) until we have a better understanding of the state
of SGID issues.

Thanks,
Amir.