linux-kernel - [PATCH net 4/5] net/mlx5e: Fix wraparound in rate limiting for values above 255 Gbps

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Message-ID: <1762681073-1084058-5-git-send-email-tariqt@nvidia.com>
Date: Sun, 9 Nov 2025 11:37:52 +0200
From: Tariq Toukan <tariqt@...dia.com>
To: Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>
CC: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
	Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Gal Pressman <gal@...dia.com>
Subject: [PATCH net 4/5] net/mlx5e: Fix wraparound in rate limiting for values above 255 Gbps

From: Gal Pressman <gal@...dia.com>

Add validation to reject rates exceeding 255 Gbps that would overflow
the 8 bits max bandwidth field.

Fixes: d8880795dabf ("net/mlx5e: Implement DCBNL IEEE max rate")
Signed-off-by: Gal Pressman <gal@...dia.com>
Reviewed-by: Nimrod Oren <noren@...dia.com>
Signed-off-by: Tariq Toukan <tariqt@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c b/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
index 345614471052..d88a48210fdc 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
@@ -596,11 +596,13 @@ static int mlx5e_dcbnl_ieee_setmaxrate(struct net_device *netdev,
 	u8 max_bw_value[IEEE_8021QAZ_MAX_TCS];
 	u8 max_bw_unit[IEEE_8021QAZ_MAX_TCS];
 	__u64 upper_limit_mbps;
+	__u64 upper_limit_gbps;
 	int i;
 
 	memset(max_bw_value, 0, sizeof(max_bw_value));
 	memset(max_bw_unit, 0, sizeof(max_bw_unit));
 	upper_limit_mbps = 255 * MLX5E_100MB;
+	upper_limit_gbps = 255 * MLX5E_1GB;
 
 	for (i = 0; i <= mlx5_max_tc(mdev); i++) {
 		if (!maxrate->tc_maxrate[i]) {
@@ -612,10 +614,16 @@ static int mlx5e_dcbnl_ieee_setmaxrate(struct net_device *netdev,
 						  MLX5E_100MB);
 			max_bw_value[i] = max_bw_value[i] ? max_bw_value[i] : 1;
 			max_bw_unit[i]  = MLX5_100_MBPS_UNIT;
-		} else {
+		} else if (max_bw_value[i] <= upper_limit_gbps) {
 			max_bw_value[i] = div_u64(maxrate->tc_maxrate[i],
 						  MLX5E_1GB);
 			max_bw_unit[i]  = MLX5_GBPS_UNIT;
+		} else {
+			netdev_err(netdev,
+				   "tc_%d maxrate %llu Kbps exceeds limit %llu\n",
+				   i, maxrate->tc_maxrate[i],
+				   upper_limit_gbps);
+			return -EINVAL;
 		}
 	}
 
-- 
2.31.1