IB/uverbs: Prevent reregistration of DM_MR to regular MR

This patch adds a check in the ib_uverbs_rereg_mr flow to make
sure there's no attempt to rereg a device memory MR to regular MR.
In such case the command will fail with -EINVAL status.

fixes: be934cca ("IB/uverbs: Add device memory registration ioctl support")
Signed-off-by: Ariel Levkovich <lariel@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -765,6 +765,11 @@ ssize_t ib_uverbs_rereg_mr(struct ib_uverbs_file *file,
 
 	mr = uobj->object;
 
+	if (mr->dm) {
+		ret = -EINVAL;
+		goto put_uobjs;
+	}
+
 	if (cmd.flags & IB_MR_REREG_ACCESS) {
 		ret = ib_check_mr_access(cmd.access_flags);
 		if (ret)