[PATCH] mfd: db8500-prcmu: replace deprecated strncpy with strscpy

[PATCH] mfd: db8500-prcmu: replace deprecated strncpy with strscpy

[Justin Stitt]

`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 project_name to be NUL-terminated based on its use with
pr_info:
| 	pr_info("PRCMU firmware: %s(%d), version %d.%d.%d\n",
| 		fw_info.version.project_name,
| 		fw_info.version.project,
| 		fw_info.version.api_version,
| 		fw_info.version.func_version,
| 		fw_info.version.errata);

Moreover, NUL-padding does not seem to be needed.

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.

Let's also change `PRCMU_FW_PROJECT_NAME_LEN` to just
sizeof(fw_info.version.project_name) as this is more idiomatic strscpy
usage.

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@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
 drivers/mfd/db8500-prcmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/db8500-prcmu.c b/drivers/mfd/db8500-prcmu.c
index 27a881da4d6e..5b3e355e78f6 100644
--- a/drivers/mfd/db8500-prcmu.c
+++ b/drivers/mfd/db8500-prcmu.c
@@ -2639,9 +2639,9 @@ static void dbx500_fw_version_init(struct device_node *np)
 	fw_info.version.api_version = (version >> 8) & 0xFF;
 	fw_info.version.func_version = (version >> 16) & 0xFF;
 	fw_info.version.errata = (version >> 24) & 0xFF;
-	strncpy(fw_info.version.project_name,
+	strscpy(fw_info.version.project_name,
 		fw_project_name(fw_info.version.project),
-		PRCMU_FW_PROJECT_NAME_LEN);
+		sizeof(fw_info.version.project_name));
 	fw_info.valid = true;
 	pr_info("PRCMU firmware: %s(%d), version %d.%d.%d\n",
 		fw_info.version.project_name,

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230927-strncpy-drivers-mfd-db8500-prcmu-c-aeeff615bc80

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

Re: [PATCH] mfd: db8500-prcmu: replace deprecated strncpy with strscpy

[Linus Walleij]

Hi Justin,

thanks for your patch!

On Wed, Sep 27, 2023 at 7:10 AM Justin Stitt <justinstitt@google.com> 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 project_name to be NUL-terminated based on its use with
> pr_info:
> |       pr_info("PRCMU firmware: %s(%d), version %d.%d.%d\n",
> |               fw_info.version.project_name,
> |               fw_info.version.project,
> |               fw_info.version.api_version,
> |               fw_info.version.func_version,
> |               fw_info.version.errata);
>
> Moreover, NUL-padding does not seem to be needed.
>
> 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.
>
> Let's also change `PRCMU_FW_PROJECT_NAME_LEN` to just
> sizeof(fw_info.version.project_name) as this is more idiomatic strscpy
> usage.
>
> 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Well analyzed, well patched, what can I say! Hats off.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: (subset) [PATCH] mfd: db8500-prcmu: replace deprecated strncpy with strscpy

[Lee Jones]

On Wed, 27 Sep 2023 05:10:54 +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 project_name to be NUL-terminated based on its use with
> pr_info:
> | 	pr_info("PRCMU firmware: %s(%d), version %d.%d.%d\n",
> | 		fw_info.version.project_name,
> | 		fw_info.version.project,
> | 		fw_info.version.api_version,
> | 		fw_info.version.func_version,
> | 		fw_info.version.errata);
> 
> [...]

Applied, thanks!

[1/1] mfd: db8500-prcmu: replace deprecated strncpy with strscpy
      commit: 5f0c4e32e8da434a83dd74a08e477c11e7efc6f7

--
Lee Jones [李琼斯]