IB/uverbs: Return correct error for invalid PD in register MR

If no matching PD is found in ib_uverbs_reg_mr(), then the function
jumps to err_release without setting the return value ret.  This means
that ret will hold the return value of the call to ib_umem_get() a few
lines earlier; if the function reaches the point where it looks for
the PD, we know that ib_umem_get() must have returned 0, so
ib_uverbs_reg_mr() ends up return 0 for a bad PD ID.  Fix this by
setting ret to -EINVAL before jumping to the exit path when no PD is
found.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -622,8 +622,10 @@ ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
 	obj->umem.virt_base = cmd.hca_va;
 
 	pd = idr_read_pd(cmd.pd_handle, file->ucontext);
-	if (!pd)
+	if (!pd) {
+		ret = -EINVAL;
 		goto err_release;
+	}
 
 	mr = pd->device->reg_user_mr(pd, &obj->umem, cmd.access_flags, &udata);
 	if (IS_ERR(mr)) {