IB/mlx5: Fix out-of-bound access

When we initialize buffer to create SRQ in kernel,
the number of pages was less than actually used in
following mlx5_fill_page_array().

Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters")
Cc: <stable@vger.kernel.org> # v3.10+
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/srq.c

@@ -165,8 +165,6 @@ static int create_srq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_srq *srq,
 	int err;
 	int i;
 	struct mlx5_wqe_srq_next_seg *next;
-	int page_shift;
-	int npages;
 
 	err = mlx5_db_alloc(dev->mdev, &srq->db);
 	if (err) {
@@ -179,7 +177,6 @@ static int create_srq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_srq *srq,
 		err = -ENOMEM;
 		goto err_db;
 	}
-	page_shift = srq->buf.page_shift;
 
 	srq->head    = 0;
 	srq->tail    = srq->msrq.max - 1;
@@ -191,10 +188,8 @@ static int create_srq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_srq *srq,
 			cpu_to_be16((i + 1) & (srq->msrq.max - 1));
 	}
 
-	npages = DIV_ROUND_UP(srq->buf.npages, 1 << (page_shift - PAGE_SHIFT));
-	mlx5_ib_dbg(dev, "buf_size %d, page_shift %d, npages %d, calc npages %d\n",
-		    buf_size, page_shift, srq->buf.npages, npages);
-	in->pas = mlx5_vzalloc(sizeof(*in->pas) * npages);
+	mlx5_ib_dbg(dev, "srq->buf.page_shift = %d\n", srq->buf.page_shift);
+	in->pas = mlx5_vzalloc(sizeof(*in->pas) * srq->buf.npages);
 	if (!in->pas) {
 		err = -ENOMEM;
 		goto err_buf;
@@ -208,7 +203,7 @@ static int create_srq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_srq *srq,
 	}
 	srq->wq_sig = !!srq_signature;
 
-	in->log_page_size = page_shift - MLX5_ADAPTER_PAGE_SHIFT;
+	in->log_page_size = srq->buf.page_shift - MLX5_ADAPTER_PAGE_SHIFT;
 	if (MLX5_CAP_GEN(dev->mdev, cqe_version) == MLX5_CQE_VERSION_V1 &&
 	    in->type == IB_SRQT_XRC)
 		in->user_index = MLX5_IB_DEFAULT_UIDX;