linux-hardening - [PATCH] net: ax88796c: replace deprecated strncpy with strscpy

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Message-ID: <20231005-strncpy-drivers-net-ethernet-asix-ax88796c_ioctl-c-v1-1-6fafdc38b170@google.com>
Date: Thu, 05 Oct 2023 01:06:26 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: "Łukasz Stelmach" <l.stelmach@...sung.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] net: ax88796c: replace deprecated strncpy with strscpy

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on the destination buffer without
unnecessarily NUL-padding.

It should be noted that there doesn't currently exist a bug here as
DRV_NAME is a small string literal which means no overread bugs are
present.

Also to note, other ethernet drivers are using strscpy in a similar
pattern:
|       dec/tulip/tulip_core.c
|       861:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       8390/ax88796.c
|       582:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       dec/tulip/dmfe.c
|       1077:   strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       8390/etherh.c
|       558:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));

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.
---
 drivers/net/ethernet/asix/ax88796c_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/asix/ax88796c_ioctl.c b/drivers/net/ethernet/asix/ax88796c_ioctl.c
index 916ae380a004..7d2fe2e5af92 100644
--- a/drivers/net/ethernet/asix/ax88796c_ioctl.c
+++ b/drivers/net/ethernet/asix/ax88796c_ioctl.c
@@ -24,7 +24,7 @@ static void
 ax88796c_get_drvinfo(struct net_device *ndev, struct ethtool_drvinfo *info)
 {
 	/* Inherit standard device info */
-	strncpy(info->driver, DRV_NAME, sizeof(info->driver));
+	strscpy(info->driver, DRV_NAME, sizeof(info->driver));
 }
 
 static u32 ax88796c_get_msglevel(struct net_device *ndev)

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231005-strncpy-drivers-net-ethernet-asix-ax88796c_ioctl-c-56af20b7d992

Best regards,
--
Justin Stitt <justinstitt@...gle.com>