IB/umem: fix reference count leak in ib_umem_odp_get()

Add missing mmput() on error path to avoid ref-count leak.

This problem is introduced by 79bb5b7ee1 ("RDMA/umem: Fix missing mmap_sem in get umem ODP call")
and resolved by f27a0d50a4bc ("RDMA/umem: Use umem->owning_mm inside ODP").
So, it's only needed in stable-4.14 and stable-4.19.

Fixes: 79bb5b7ee1 ("RDMA/umem: Fix missing mmap_sem in get umem ODP call")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/infiniband/core/umem_odp.c

@@ -306,7 +306,8 @@ int ib_umem_odp_get(struct ib_ucontext *context, struct ib_umem *umem,
 		vma = find_vma(mm, ib_umem_start(umem));
 		if (!vma || !is_vm_hugetlb_page(vma)) {
 			up_read(&mm->mmap_sem);
-			return -EINVAL;
+			ret_val = -EINVAL;
+			goto out_mm;
 		}
 		h = hstate_vma(vma);
 		umem->page_shift = huge_page_shift(h);