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

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Message-ID: <20230927-strncpy-drivers-mfd-db8500-prcmu-c-v1-1-db9693f92a68@google.com>
Date:   Wed, 27 Sep 2023 05:10:54 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Lee Jones <lee@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] mfd: db8500-prcmu: 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 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@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.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@...gle.com>