On Tue, Feb 16, 2016 at 11:45:33AM -0800, Maxim Patlasov wrote:
> propagate_one(m) calculates "type" argument for copy_tree() like this:
>
> > if (m->mnt_group_id == last_dest->mnt_group_id) {
> > type = CL_MAKE_SHARED;
> > } else {
> > type = CL_SLAVE;
> > if (IS_MNT_SHARED(m))
> > type |= CL_MAKE_SHARED;
> > }
>
> The "type" argument then governs clone_mnt() behavior with respect to flags
> and mnt_master of new mount. When we iterate through a slave group, it is
> possible that both current "m" and "last_dest" are not shared (although,
> both are slaves, i.e. have non-NULL mnt_master-s). Then the comparison
> above erroneously makes new mount shared and sets its mnt_master to
> last_source->mnt_master. The patch fixes the problem by handling zero
> mnt_group_id-s as though they are unequal.
>
> The similar problem exists in the implementation of "else" clause above
> when we have to ascend upward in the master/slave tree by calling:
>
> > last_source = last_source->mnt_master;
> > last_dest = last_source->mnt_parent;
>
> proper number of times. The last step is governed by
> "n->mnt_group_id != last_dest->mnt_group_id" condition that may lie if
> both are zero. The patch fixes this case in the same way as the former one.
Mind putting together a reproducer?
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