net/rds: fix possible cp null dereference

cp might be null, calling cp->cp_conn would produce null dereference

[Simon Horman adds:]

Analysis:

* cp is a parameter of __rds_rdma_map and is not reassigned.

* The following call-sites pass a NULL cp argument to __rds_rdma_map()

  - rds_get_mr()
  - rds_get_mr_for_dest

* Prior to the code above, the following assumes that cp may be NULL
  (which is indicative, but could itself be unnecessary)

	trans_private = rs->rs_transport->get_mr(
		sg, nents, rs, &mr->r_key, cp ? cp->cp_conn : NULL,
		args->vec.addr, args->vec.bytes,
		need_odp ? ODP_ZEROBASED : ODP_NOT_NEEDED);

* The code modified by this patch is guarded by IS_ERR(trans_private),
  where trans_private is assigned as per the previous point in this analysis.

  The only implementation of get_mr that I could locate is rds_ib_get_mr()
  which can return an ERR_PTR if the conn (4th) argument is NULL.

* ret is set to PTR_ERR(trans_private).
  rds_ib_get_mr can return ERR_PTR(-ENODEV) if the conn (4th) argument is NULL.
  Thus ret may be -ENODEV in which case the code in question will execute.

Conclusion:
* cp may be NULL at the point where this patch adds a check;
  this patch does seem to address a possible bug

Fixes: c055fc00c07b ("net/rds: fix WARNING in rds_conn_connect_if_down")
Cc: [email protected] # v4.19+
Signed-off-by: Mahmoud Adam <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index a4e3c5de998be4c756cb0dc423ee9a7e7fa3e1a9..00dbcd4d28e68097c612c628b7d4193124be4c9c 100644 (file)
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -302,7 +302,7 @@ static int __rds_rdma_map(struct rds_sock *rs, struct rds_get_mr_args *args,
                }
                ret = PTR_ERR(trans_private);
                /* Trigger connection so that its ready for the next retry */
-               if (ret == -ENODEV)
+               if (ret == -ENODEV && cp)
                        rds_conn_connect_if_down(cp->cp_conn);
                goto out;
        }