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);
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.
We can also use sizeof() instead of a length macro as this more closely
ties the maximum buffer size to the destination buffer. Do this for two
instances.
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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v3:
- swap another instance of MII_BUS_ID_SIZE to sizeof() (thanks Russell)
- rebase onto mainline bee0e7762ad2c602
- Link to v2: https://lore.kernel.org/r/20231207-strncpy-drivers-net-mdio-mdio-gpio-c-v2-1-c28d52dd3dfe@google.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"superseded" label being improperly applied.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 | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/mdio/mdio-gpio.c b/drivers/net/mdio/mdio-gpio.c
index 897b88c50bbb..778db310a28d 100644
--- a/drivers/net/mdio/mdio-gpio.c
+++ b/drivers/net/mdio/mdio-gpio.c
@@ -123,9 +123,9 @@ static struct mii_bus *mdio_gpio_bus_init(struct device *dev,
new_bus->parent = dev;
if (bus_id != -1)
- snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
+ snprintf(new_bus->id, sizeof(new_bus->id), "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: bee0e7762ad2c6025b9f5245c040fcc36ef2bde8
change-id: 20231012-strncpy-drivers-net-mdio-mdio-gpio-c-bddd9ed0c630
Best regards,
--
Justin Stitt <[email protected]>
On Mon, Dec 11, 2023 at 07:10:00PM +0000, 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 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);
>
> 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.
>
> We can also use sizeof() instead of a length macro as this more closely
> ties the maximum buffer size to the destination buffer. Do this for two
> instances.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Reviewed-by: Russell King (Oracle) <[email protected]>
Thanks!
--
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FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
On Mon, Dec 11, 2023 at 07:10:00PM +0000, 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 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);
>
> 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.
>
> We can also use sizeof() instead of a length macro as this more closely
> ties the maximum buffer size to the destination buffer. Do this for two
> instances.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Looks like a clean replacement. (And a nice sizeof cleanup.)
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
Hello:
This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:
On Mon, 11 Dec 2023 19:10:00 +0000 you 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 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);
>
> [...]
Here is the summary with links:
- [v3] net: mdio-gpio: replace deprecated strncpy with strscpy
https://git.kernel.org/netdev/net-next/c/79ac11393328
You are awesome, thank you!
--
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