linux-kernel - [PATCH] ath5k: replace deprecated strncpy with strscpy

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Message-ID: <20231013-strncpy-drivers-net-wireless-ath-ath5k-led-c-v1-1-3acb0b5a21f2@google.com>
Date:   Fri, 13 Oct 2023 20:53:33 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Jiri Slaby <jirislaby@...nel.org>,
        Nick Kossifidis <mickflemm@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kalle Valo <kvalo@...nel.org>
Cc:     linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] ath5k: 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 led->name to be NUL-terminated based on the presence of a
manual NUL-byte assignment.

This NUL-byte assignment was added in Commit daf9669bea30aa22 ("ath5k:
ensure led name is null terminated"). If strscpy() had existed and had
been used back when this code was written then potential bugs and the
need to manually NUL-terminate could have been avoided. Since we now
have the technology, let's use it :)

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. If NUL-padding is required let's opt
for strscpy_pad().

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/net/wireless/ath/ath5k/led.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath5k/led.c b/drivers/net/wireless/ath/ath5k/led.c
index 33e9928af363..439052984796 100644
--- a/drivers/net/wireless/ath/ath5k/led.c
+++ b/drivers/net/wireless/ath/ath5k/led.c
@@ -131,8 +131,7 @@ ath5k_register_led(struct ath5k_hw *ah, struct ath5k_led *led,
 	int err;

 	led->ah = ah;
-	strncpy(led->name, name, sizeof(led->name));
-	led->name[sizeof(led->name)-1] = 0;
+	strscpy(led->name, name, sizeof(led->name));
 	led->led_dev.name = led->name;
 	led->led_dev.default_trigger = trigger;
 	led->led_dev.brightness_set = ath5k_led_brightness_set;

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231013-strncpy-drivers-net-wireless-ath-ath5k-led-c-12487cee93be

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