Re: [rds-devel] KASAN: null-ptr-deref Read in rds_ib_get_mr

[Yanjun Zhu]

On 2018/5/11 18:46, Sowmini Varadhan wrote:
> On (05/11/18 15:48), Yanjun Zhu wrote:
> > diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
> > index e678699..2228b50 100644
> > --- a/net/rds/ib_rdma.c
> > +++ b/net/rds/ib_rdma.c
> > @@ -539,11 +539,17 @@ void rds_ib_flush_mrs(void)
> >     void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
> >                                          struct rds_sock *rs, u32 *key_ret)
> >     {
> > -             struct rds_ib_device *rds_ibdev;
> > +             struct rds_ib_device *rds_ibdev = NULL;
> >                  struct rds_ib_mr *ibmr = NULL;
> > -             struct rds_ib_connection *ic = rs->rs_conn->c_transport_data;
> > +             struct rds_ib_connection *ic = NULL;
> >                  int ret;
> >
> > +             if (rs->rs_bound_addr == 0) {
> > +                             ret = -EPERM;
> > +                             goto out;
> > +             }
> > +
> > +             ic = rs->rs_conn->c_transport_data;
> >                  rds_ibdev = rds_ib_get_device(rs->rs_bound_addr);
> >                  if (!rds_ibdev) {
> >                                  ret = -ENODEV;
> >
> > I made this raw patch. If you can reproduce this bug, please make tests
> > with it.
> I dont think this solves the problem, I think it
> just changes the timing under which it can still happen.
>
> what if the rds_remove_bound() in rds_bind() happens after the check
> for if (rs->rs_bound_addr == 0) added above by the patch
>
> I believe you need some type of synchronization (either
> through mutex, or some atomic flag in the rs or similar) to make
> sure rds_bind() and rds_ib_get_mr() are mutually exclusive.
Sure. I agree with you. Maybe mutex is a good choice.

Zhu Yanjun
> --Sowmini
>