Re: [PATCH for-next 02/13] RDMA/rtrs-srv: Fix use-after-free during session establishment

[Leon Romanovsky <leon@kernel.org>]

On Mon, Aug 12, 2024 at 12:52:25PM +0200, Jinpu Wang wrote:
> Hi,
> 
> On Sun, Aug 11, 2024 at 10:41 AM Leon Romanovsky <leon@kernel.org> wrote:
> >
> > On Fri, Aug 09, 2024 at 03:15:27PM +0200, Md Haris Iqbal wrote:
> > > From: Jack Wang <jinpu.wang@ionos.com>
> > >
> > > In case of error happening during session stablishment, close_work is
> > > running. A new RDMA CM event may arrive since we don't destroy cm_id
> > > before destroying qp. To fix this, we first destroy cm_id after drain_qp,
> > > so no new RDMA CM event will arrive afterwards.
> > >
> > > Fixes: 9cb837480424 ("RDMA/rtrs: server: main functionality")
> > > Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
> > > Signed-off-by: Grzegorz Prajsner <grzegorz.prajsner@ionos.com>
> > > Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
> > > ---
> > >  drivers/infiniband/ulp/rtrs/rtrs-srv.c | 2 +-
> > >  drivers/infiniband/ulp/rtrs/rtrs.c     | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > index fb67b58a7f62..90ea25ad6720 100644
> > > --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c
> > > @@ -1540,6 +1540,7 @@ static void rtrs_srv_close_work(struct work_struct *work)
> > >               con = to_srv_con(srv_path->s.con[i]);
> > >               rdma_disconnect(con->c.cm_id);
> > >               ib_drain_qp(con->c.qp);
> > > +             rdma_destroy_id(con->c.cm_id);
> > >       }
> > >
> > >       /*
> > > @@ -1564,7 +1565,6 @@ static void rtrs_srv_close_work(struct work_struct *work)
> > >                       continue;
> > >               con = to_srv_con(srv_path->s.con[i]);
> > >               rtrs_cq_qp_destroy(&con->c);
> > > -             rdma_destroy_id(con->c.cm_id);
> > >               kfree(con);
> > >       }
> > >       rtrs_ib_dev_put(srv_path->s.dev);
> > > diff --git a/drivers/infiniband/ulp/rtrs/rtrs.c b/drivers/infiniband/ulp/rtrs/rtrs.c
> > > index 4e17d546d4cc..44167fd1c958 100644
> > > --- a/drivers/infiniband/ulp/rtrs/rtrs.c
> > > +++ b/drivers/infiniband/ulp/rtrs/rtrs.c
> > > @@ -318,7 +318,7 @@ EXPORT_SYMBOL_GPL(rtrs_cq_qp_create);
> > >  void rtrs_cq_qp_destroy(struct rtrs_con *con)
> > >  {
> > >       if (con->qp) {
> > > -             rdma_destroy_qp(con->cm_id);
> > > +             ib_destroy_qp(con->qp);
> >
> > You created that QP with rdma_create_qp() and you should destroy it with rdma_destroy_qp().
> We can't do it, as we move rdma_destroy_id before rtrs_cq_qp_destroy,
> if we still call rdma_destroy_qp, which will lead to use after free as
> cm_id could already be free-ed.

It is a hint that you are doing something wrong.

Thanks

> 
> >
> > Thanks
> Thx!
> >
> > >               con->qp = NULL;
> > >       }
> > >       destroy_cq(con);
> > > --
> > > 2.25.1
> > >
>