On Tue, 21 Aug 2007 17:21:28 -0400
Josef Sipek <jsipek@xxxxxxxxxxxxxxxxx> wrote:
> On Tue, Aug 21, 2007 at 07:35:51AM -0400, Jeff Layton wrote:
> > On Tue, 21 Aug 2007 15:35:08 +1000
> > Timothy Shimmin <tes@xxxxxxx> wrote:
> >
> > > Jeff Layton wrote:
> > > > This should fix all of the filesystems in the mainline kernels to handle
> > > > ATTR_KILL_SUID and ATTR_KILL_SGID correctly. For most of them, this is
> > > > just a matter of making sure that they call generic_attrkill early in
> > > > the setattr inode op.
> > > >
> > > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > > > ---
> > > > fs/xfs/linux-2.6/xfs_iops.c | 5 ++++-
> > > > --- a/fs/xfs/linux-2.6/xfs_iops.c
> > > > +++ b/fs/xfs/linux-2.6/xfs_iops.c
> > > > @@ -651,12 +651,15 @@ xfs_vn_setattr(
> > > > struct iattr *attr)
> > > > {
> > > > struct inode *inode = dentry->d_inode;
> > > > - unsigned int ia_valid = attr->ia_valid;
> > > > + unsigned int ia_valid;
> > > > bhv_vnode_t *vp = vn_from_inode(inode);
> > > > bhv_vattr_t vattr = { 0 };
> > > > int flags = 0;
> > > > int error;
> > > >
> > > > + generic_attrkill(inode->i_mode, attr);
> > > > + ia_valid = attr->ia_valid;
> > > > +
> > > > if (ia_valid & ATTR_UID) {
> > > > vattr.va_mask |= XFS_AT_UID;
> > > > vattr.va_uid = attr->ia_uid;
> > >
> > > Looks reasonable to me for XFS.
> > > Acked-by: Tim Shimmin <tes@xxxxxxx>
> > >
> > > So before, this clearing would happen directly in notify_change()
> > > and now this won't happen until notify_change() calls i_op->setattr
> > > which for a particular fs it can call generic_attrkill() to do it.
> > > So I guess for the cases where i_op->setattr is called outside of
> > > via notify_change, we don't normally have ATTR_KILL_SUID/SGID
> > > set so that nothing will happen there?
> >
> > Right. If neither ATTR_KILL bit is set then generic_attrkill is a
> > noop.
> >
> > > I guess just wondering the effect with having the code on all
> > > setattr's. (I'm not familiar with the code path)
> > >
> >
> > These bits are referenced in very few places in the current kernel
> > tree -- mostly in the VFS layer. The *only* place I see that they
> > actually get interpreted into a mode change is in notify_change. So
> > places that call setattr ops w/o going through notify_change are
> > not likely to have those bits set.
> >
> > But hypothetically, if a fs did set ATTR_KILL_* and call setattr
> > directly, then the setattr would now include a mode change that
> > clears setuid or setgid bits where it may not have before.
>
I should probably clarify -- in the hypothetical situation above,
the setattr function would have to call generic_attrkill (as most
filesystems should do with this change).
> It almost sounds like an argument for a new inode op (NULL would use
> generic_attr_kill).
>
That's not a bad idea at all. I suppose that would be easier than
modifying every fs like this, and it does seem like it might be
cleaner. I need to mull it over, but that might be the best
solution.
--
Jeff Layton <jlayton@xxxxxxxxxx>
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