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Message-ID: <20231207-strncpy-drivers-net-mdio-mdio-gpio-c-v2-1-c28d52dd3dfe@google.com>
Date: Thu, 07 Dec 2023 21:54:31 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
Russell King <linux@...linux.org.uk>, "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 v2] net: mdio-gpio: 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.
We expect new_bus->id to be NUL-terminated but not NUL-padded based on
its prior assignment through snprintf:
| snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
We can also use sizeof() instead of a length macro as this more closely
ties the maximum buffer size to the destination buffer.
Due to this, 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>
---
Changes in v2:
- change subject line as it was causing problems in patchwork with
"superseded" label being improperly applied.
- update commit msg with rationale around sizeof() (thanks Kees)
- Link to v1 (lore): https://lore.kernel.org/r/20231012-strncpy-drivers-net-mdio-mdio-gpio-c-v1-1-ab9b06cfcdab@google.com
- Link to v1 (patchwork): https://patchwork.kernel.org/project/netdevbpf/patch/20231012-strncpy-drivers-net-mdio-mdio-gpio-c-v1-1-ab9b06cfcdab@google.com/
- Link to other patch with same subject message: https://patchwork.kernel.org/project/netdevbpf/patch/20231012-strncpy-drivers-net-phy-mdio_bus-c-v1-1-15242e6f9ec4@google.com/
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/net/mdio/mdio-gpio.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/mdio/mdio-gpio.c b/drivers/net/mdio/mdio-gpio.c
index 0fb3c2de0845..a1718d646504 100644
--- a/drivers/net/mdio/mdio-gpio.c
+++ b/drivers/net/mdio/mdio-gpio.c
@@ -125,7 +125,7 @@ static struct mii_bus *mdio_gpio_bus_init(struct device *dev,
if (bus_id != -1)
snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
else
- strncpy(new_bus->id, "gpio", MII_BUS_ID_SIZE);
+ strscpy(new_bus->id, "gpio", sizeof(new_bus->id));
if (pdata) {
new_bus->phy_mask = pdata->phy_mask;
---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231012-strncpy-drivers-net-mdio-mdio-gpio-c-bddd9ed0c630
Best regards,
--
Justin Stitt <justinstitt@...gle.com>
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