netdev - [PATCH net v1 1/2] net/mlx5e: Correct snprintf truncation handling for fw

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Date: Tue, 21 Nov 2023 15:00:21 -0800
From: Rahul Rameshbabu <rrameshbabu@...dia.com>
To: netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Saeed Mahameed <saeed@...nel.org>,
	Gal Pressman <gal@...dia.com>,
	Dragos Tatulea <dtatulea@...dia.com>,
	David Laight <David.Laight@...LAB.COM>,
	Rahul Rameshbabu <rrameshbabu@...dia.com>
Subject: [PATCH net v1 1/2] net/mlx5e: Correct snprintf truncation handling for fw_version buffer

snprintf returns the length of the formatted string, excluding the trailing
null, without accounting for truncation. This means that is the return
value is greater than or equal to the size parameter, the fw_version string
was truncated.

Reported-by: David Laight <David.Laight@...LAB.COM>
Closes: https://lore.kernel.org/netdev/81cae734ee1b4cde9b380a9a31006c1a@AcuMS.aculab.com/
Link: https://docs.kernel.org/core-api/kernel-api.html#c.snprintf
Fixes: 41e63c2baa11 ("net/mlx5e: Check return value of snprintf writing to fw_version buffer")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
index 792a0ea544cd..c7c1b667b105 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_ethtool.c
@@ -49,7 +49,7 @@ void mlx5e_ethtool_get_drvinfo(struct mlx5e_priv *priv,
 	count = snprintf(drvinfo->fw_version, sizeof(drvinfo->fw_version),
 			 "%d.%d.%04d (%.16s)", fw_rev_maj(mdev),
 			 fw_rev_min(mdev), fw_rev_sub(mdev), mdev->board_id);
-	if (count == sizeof(drvinfo->fw_version))
+	if (count >= sizeof(drvinfo->fw_version))
 		snprintf(drvinfo->fw_version, sizeof(drvinfo->fw_version),
 			 "%d.%d.%04d", fw_rev_maj(mdev),
 			 fw_rev_min(mdev), fw_rev_sub(mdev));
-- 
2.40.1