re: net/mlx5: IPsec, Refactor SA handle creation and destruction

[Colin Ian King <colin.king@canonical.com>]

Hi,

Static analysis with Coverity has detected a potential issue with the
following commit:

commit 7dfee4b1d79e1800818abcfb47747b162c9a2d31
Author: Raed Salem <raeds@mellanox.com>
Date:   Wed Oct 23 17:04:13 2019 +0300

    net/mlx5: IPsec, Refactor SA handle creation and destruction

The issue is in mlx5_fpga_is_ipsec_device() in
drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c as follows:


710  Bitwise-and with zero
     bit_and_with_zero: accel_xfrm->attrs.action &
MLX5_ACCEL_ESP_ACTION_DECRYPT is always 0.  This occurs as the logical
operand of if.

711        if (accel_xfrm->attrs.action & MLX5_ACCEL_ESP_ACTION_DECRYPT) {
Logically dead code (DEADCODE)

712                err = ida_simple_get(&fipsec->halloc, 1, 0, GFP_KERNEL);
713                if (err < 0) {
714                        context = ERR_PTR(err);
715                        goto exists;
716                }
717
718                sa_ctx->sa_handle = err;
719                if (sa_handle)
720                        *sa_handle = sa_ctx->sa_handle;
721        }

in include/linux/mlx5/accel.h MLX5_ACCEL_ESP_ACTION_DECRYPT is defined
as zero:

50 enum mlx5_accel_esp_action {
51        MLX5_ACCEL_ESP_ACTION_DECRYPT,
52        MLX5_ACCEL_ESP_ACTION_ENCRYPT,
53 };


I believe there are some other instances of this bit-wise and-ing with
zero, e.g. in mlx5_fpga_ipsec_release_sa_ctx() we have:

855     if (sa_ctx->fpga_xfrm->accel_xfrm.attrs.action &
856         MLX5_ACCEL_ESP_ACTION_DECRYPT)

Colin