linux/dim: Fix overflow in dim calculation

While using net_dim, a dim_sample was used without ever initializing the
comps value. Added use of DIV_ROUND_DOWN_ULL() to prevent potential
overflow, it should not be a problem to save the final result in an int
because after the division by epms the value should not be larger than a
few thousand.

[ 1040.127124] UBSAN: Undefined behaviour in lib/dim/dim.c:78:23
[ 1040.130118] signed integer overflow:
[ 1040.131643] 134718714 * 100 cannot be represented in type 'int'

Fixes: 398c2b05bbee ("linux/dim: Add completions count to dim_sample")
Signed-off-by: Yamin Friedman <[e-mail]>
Signed-off-by: Leon Romanovsky <[e-mail]>
Acked-by: Saeed Mahameed <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/broadcom/bcmsysport.c

···
 {
 	struct bcm_sysport_priv *priv =
 		container_of(napi, struct bcm_sysport_priv, napi);
-	struct dim_sample dim_sample;
+	struct dim_sample dim_sample = {};
 	unsigned int work_done = 0;
 
 	work_done = bcm_sysport_desc_rx(priv, budget);

drivers/net/ethernet/broadcom/bnxt/bnxt.c

···
 		}
 	}
 	if (bp->flags & BNXT_FLAG_DIM) {
-		struct dim_sample dim_sample;
+		struct dim_sample dim_sample = {};
 
 		dim_update_sample(cpr->event_ctr,
 				  cpr->rx_packets,

drivers/net/ethernet/broadcom/genet/bcmgenet.c

···
 {
 	struct bcmgenet_rx_ring *ring = container_of(napi,
 			struct bcmgenet_rx_ring, napi);
-	struct dim_sample dim_sample;
+	struct dim_sample dim_sample = {};
 	unsigned int work_done;
 
 	work_done = bcmgenet_desc_rx(ring, budget);

drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c

···
 static void mlx5e_handle_tx_dim(struct mlx5e_txqsq *sq)
 {
 	struct mlx5e_sq_stats *stats = sq->stats;
-	struct dim_sample dim_sample;
+	struct dim_sample dim_sample = {};
 
 	if (unlikely(!test_bit(MLX5E_SQ_STATE_AM, &sq->state)))
 		return;
···
 static void mlx5e_handle_rx_dim(struct mlx5e_rq *rq)
 {
 	struct mlx5e_rq_stats *stats = rq->stats;
-	struct dim_sample dim_sample;
+	struct dim_sample dim_sample = {};
 
 	if (unlikely(!test_bit(MLX5E_RQ_STATE_AM, &rq->state)))
 		return;

lib/dim/dim.c

···
 					delta_us);
 	curr_stats->cpms = DIV_ROUND_UP(ncomps * USEC_PER_MSEC, delta_us);
 	if (curr_stats->epms != 0)
-		curr_stats->cpe_ratio =
-				(curr_stats->cpms * 100) / curr_stats->epms;
+		curr_stats->cpe_ratio = DIV_ROUND_DOWN_ULL(
+			curr_stats->cpms * 100, curr_stats->epms);
 	else
 		curr_stats->cpe_ratio = 0;