linux-kernel - [PATCH] power: supply: charger-manager: replace deprecated strncpy with strscpy

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Message-ID: <20231020-strncpy-drivers-power-supply-charger-manager-c-v1-1-698f73bcad2a@google.com>
Date:   Fri, 20 Oct 2023 19:21:46 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Sebastian Reichel <sre@...nel.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] power: supply: charger-manager: 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 cm->psy_name_buf to be NUL-terminated based on its usage with
format strings:
1522: cm->charger_psy_desc.name = cm->psy_name_buf;
...
1587: dev_err(&pdev->dev, "Cannot register charger-manager with name \"%s\"\n",
1587:   cm->charger_psy_desc.name);

Moreover, NUL-padding is not required as `cm` is already zero-allocated
and thus any future NUL-byte assignments (like what strncpy() will do)
are redundant:
1437: cm = devm_kzalloc(&pdev->dev, sizeof(*cm), GFP_KERNEL);

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 opt for the more idiomatic strscpy() usage of:
strscpy(dest, src, sizeof(dest)).

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>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/power/supply/charger-manager.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/charger-manager.c b/drivers/power/supply/charger-manager.c
index 5fa6ba7f41e1..085d5277bc19 100644
--- a/drivers/power/supply/charger-manager.c
+++ b/drivers/power/supply/charger-manager.c
@@ -1516,9 +1516,11 @@ static int charger_manager_probe(struct platform_device *pdev)
 	memcpy(&cm->charger_psy_desc, &psy_default, sizeof(psy_default));
 
 	if (!desc->psy_name)
-		strncpy(cm->psy_name_buf, psy_default.name, PSY_NAME_MAX);
+		strscpy(cm->psy_name_buf, psy_default.name,
+			sizeof(cm->psy_name_buf));
 	else
-		strncpy(cm->psy_name_buf, desc->psy_name, PSY_NAME_MAX);
+		strscpy(cm->psy_name_buf, desc->psy_name,
+			sizeof(cm->psy_name_buf));
 	cm->charger_psy_desc.name = cm->psy_name_buf;
 
 	/* Allocate for psy properties because they may vary */

---
base-commit: bb55d7f7f7445abcc8db50e6a65d4315e79f75c7
change-id: 20231020-strncpy-drivers-power-supply-charger-manager-c-236767ef929c

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