net/mlx5e: Fix operation precedence bug in port timestamping napi_poll context

[ Upstream commit 3876638b2c7ebb2c9d181de1191db0de8cac143a ]

Indirection (*) is of lower precedence than postfix increment (++). Logic
in napi_poll context would cause an out-of-bound read by first increment
the pointer address by byte address space and then dereference the value.
Rather, the intended logic was to dereference first and then increment the
underlying value.

Fixes: 92214be5979c ("net/mlx5e: Update doorbell for port timestamping CQ before the software counter")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
index af3928e..803035d 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/ptp.c
@@ -213,7 +213,7 @@ static void mlx5e_ptp_handle_ts_cqe(struct mlx5e_ptpsq *ptpsq,
        mlx5e_ptpsq_mark_ts_cqes_undelivered(ptpsq, hwtstamp);
 out:
        napi_consume_skb(skb, budget);
-       md_buff[*md_buff_sz++] = metadata_id;
+       md_buff[(*md_buff_sz)++] = metadata_id;
        if (unlikely(mlx5e_ptp_metadata_map_unhealthy(&ptpsq->metadata_map)) &&
            !test_and_set_bit(MLX5E_SQ_STATE_RECOVERING, &sq->state))
                queue_work(ptpsq->txqsq.priv->wq, &ptpsq->report_unhealthy_work);