[PATCH 4.9 29/60] IB/mlx5: Fix kernel to user leak prevention logic

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eli Cohen <eli@xxxxxxxxxxxx>

commit de8d6e02efbdb259c67832ccf027d7ace9b91d5d upstream.

The logic was broken as it failed to update the response length for
architectures with PAGE_SIZE larger than 4kB. As a result further
extension of the ucontext response struct would fail.

Fixes: d69e3bcf7976 ('IB/mlx5: Mmap the HCA's core clock register to user-space')
Signed-off-by: Eli Cohen <eli@xxxxxxxxxxxx>
Reviewed-by: Matan Barak <matanb@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leon@xxxxxxxxxx>
Signed-off-by: Saeed Mahameed <saeedm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/hw/mlx5/main.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1105,13 +1105,13 @@ static struct ib_ucontext *mlx5_ib_alloc
 	 * pretend we don't support reading the HCA's core clock. This is also
 	 * forced by mmap function.
 	 */
-	if (PAGE_SIZE <= 4096 &&
-	    field_avail(typeof(resp), hca_core_clock_offset, udata->outlen)) {
-		resp.comp_mask |=
-			MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_CORE_CLOCK_OFFSET;
-		resp.hca_core_clock_offset =
-			offsetof(struct mlx5_init_seg, internal_timer_h) %
-			PAGE_SIZE;
+	if (field_avail(typeof(resp), hca_core_clock_offset, udata->outlen)) {
+		if (PAGE_SIZE <= 4096) {
+			resp.comp_mask |=
+				MLX5_IB_ALLOC_UCONTEXT_RESP_MASK_CORE_CLOCK_OFFSET;
+			resp.hca_core_clock_offset =
+				offsetof(struct mlx5_init_seg, internal_timer_h) % PAGE_SIZE;
+		}
 		resp.response_length += sizeof(resp.hca_core_clock_offset) +
 					sizeof(resp.reserved2);
 	}