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 mdiodev->modalias to be NUL-terminated based on its usage with
strcmp():
| return strcmp(mdiodev->modalias, drv->name) == 0;
Moreover, mdiodev->modalias is already zero-allocated:
| mdiodev = kzalloc(sizeof(*mdiodev), GFP_KERNEL);
... which means the NUL-padding strncpy provides is not necessary.
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: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v2:
- rename subject line as it was the same as another and was causing
problems.
- rebased onto mainline bee0e7762ad2c602
- Link to v1 (lore): https://lore.kernel.org/r/20231012-strncpy-drivers-net-phy-mdio_bus-c-v1-1-15242e6f9ec4@google.com
- Link to v1 (patchwork): https://patchwork.kernel.org/project/netdevbpf/patch/20231012-strncpy-drivers-net-phy-mdio_bus-c-v1-1-15242e6f9ec4@google.com/
- Link to collided: https://patchwork.kernel.org/project/netdevbpf/patch/20231012-strncpy-drivers-net-mdio-mdio-gpio-c-v1-1-ab9b06cfcdab@google.com/
---
Note: build-tested only.
Found with: $ rg "strncpy\("
---
drivers/net/phy/mdio_bus.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 25dcaa49ab8b..6cf73c15635b 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -506,7 +506,7 @@ static int mdiobus_create_device(struct mii_bus *bus,
if (IS_ERR(mdiodev))
return -ENODEV;
- strncpy(mdiodev->modalias, bi->modalias,
+ strscpy(mdiodev->modalias, bi->modalias,
sizeof(mdiodev->modalias));
mdiodev->bus_match = mdio_device_bus_match;
mdiodev->dev.platform_data = (void *)bi->platform_data;
---
base-commit: bee0e7762ad2c6025b9f5245c040fcc36ef2bde8
change-id: 20231012-strncpy-drivers-net-phy-mdio_bus-c-0a0d5e875712
Best regards,
--
Justin Stitt <[email protected]>
On Thu, Dec 07, 2023 at 09:57:50PM +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 mdiodev->modalias to be NUL-terminated based on its usage with
> strcmp():
> | return strcmp(mdiodev->modalias, drv->name) == 0;
>
> Moreover, mdiodev->modalias is already zero-allocated:
> | mdiodev = kzalloc(sizeof(*mdiodev), GFP_KERNEL);
> ... which means the NUL-padding strncpy provides is not necessary.
>
> 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: [email protected]
> Signed-off-by: Justin Stitt <[email protected]>
Yeah, the subject is distinct now. :)
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
Hello:
This patch was applied to netdev/net-next.git (main)
by David S. Miller <[email protected]>:
On Thu, 07 Dec 2023 21:57:50 +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 mdiodev->modalias to be NUL-terminated based on its usage with
> strcmp():
> | return strcmp(mdiodev->modalias, drv->name) == 0;
>
> [...]
Here is the summary with links:
- [v2] net: mdio_bus: replace deprecated strncpy with strscpy
https://git.kernel.org/netdev/net-next/c/1674110c0dd4
You are awesome, thank you!
--
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