linux-hardening - Re: [PATCH] net/mlx4_core: replace deprecated strncpy with strscpy

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Date: Thu, 12 Oct 2023 12:47:14 -0700
From: Saeed Mahameed <saeed@...nel.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Tariq Toukan <tariqt@...dia.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] net/mlx4_core: replace deprecated strncpy with strscpy

On 11 Oct 21:04, Justin Stitt wrote:
>`strncpy` is deprecated for use on NUL-terminated destination strings
>[1] and as such we should prefer more robust and less ambiguous string
>interfaces.
>
>We expect `dst` to be NUL-terminated based on its use with format
>strings:
>|       mlx4_dbg(dev, "Reporting Driver Version to FW: %s\n", dst);
>
>Moreover, NUL-padding is not required.
>
>Considering the above, a suitable replacement is `strscpy` [2] due to
>the fact that it guarantees NUL-termination on the destination buffer
>without unnecessarily NUL-padding.
>
>Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
>Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
>Link: https://github.com/KSPP/linux/issues/90
>Cc: linux-hardening@...r.kernel.org
>Signed-off-by: Justin Stitt <justinstitt@...gle.com>
>---
>Note: build-tested only.
>
>Found with: $ rg "strncpy\("
>---
> drivers/net/ethernet/mellanox/mlx4/fw.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/net/ethernet/mellanox/mlx4/fw.c b/drivers/net/ethernet/mellanox/mlx4/fw.c
>index fe48d20d6118..0005d9e2c2d6 100644
>--- a/drivers/net/ethernet/mellanox/mlx4/fw.c
>+++ b/drivers/net/ethernet/mellanox/mlx4/fw.c
>@@ -1967,7 +1967,7 @@ int mlx4_INIT_HCA(struct mlx4_dev *dev, struct mlx4_init_hca_param *param)
> 	if (dev->caps.flags2 & MLX4_DEV_CAP_FLAG2_DRIVER_VERSION_TO_FW) {
> 		u8 *dst = (u8 *)(inbox + INIT_HCA_DRIVER_VERSION_OFFSET / 4);
>
>-		strncpy(dst, DRV_NAME_FOR_FW, INIT_HCA_DRIVER_VERSION_SZ - 1);
>+		strscpy(dst, DRV_NAME_FOR_FW, INIT_HCA_DRIVER_VERSION_SZ);
> 		mlx4_dbg(dev, "Reporting Driver Version to FW: %s\n", dst);
> 	}
>
>
>---
>base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
>change-id: 20231011-strncpy-drivers-net-ethernet-mellanox-mlx4-fw-c-67809559dd1a
>
>Best regards,
>--
>Justin Stitt <justinstitt@...gle.com>
>

Reviewed-by: Saeed Mahameed <saeedm@...dia.com>