On Fri, 2021-04-09 at 01:35 +0000, Al Viro wrote:
> On Fri, Apr 09, 2021 at 09:15:06AM +0800, Ian Kent wrote:
> > + parent = kernfs_dentry_node(dentry->d_parent);
> > + if (parent) {
> > + const void *ns = NULL;
> > +
> > + if (kernfs_ns_enabled(parent))
> > + ns = kernfs_info(dentry->d_parent-
> > >d_sb)->ns;
>
> For any dentry d, we have d->d_parent->d_sb == d->d_sb. All
> the time.
> If you ever run into the case where that would not be true, you've
> found
> a critical bug.
Right, yes.
>
> > + kn = kernfs_find_ns(parent, dentry-
> > >d_name.name, ns);
> > + if (kn)
> > + goto out_bad;
> > + }
>
> Umm... What's to prevent a race with successful rename(2)? IOW,
> what's
> there to stabilize ->d_parent and ->d_name while we are in that
> function?
Indeed, glad you looked at this.
Now I'm wondering how kerfs_iop_rename() protects itself from
concurrent kernfs_rename_ns() ...
