[PATCH] usb: gadget: u_ether: replace deprecated strncpy with strscpy

[PATCH] usb: gadget: u_ether: 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.

Let's use the new 2-argument strscpy() as this guarantees
NUL-termination on the destination buffer and also uses the destination
buffer's size to bound the operation.

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>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/usb/gadget/function/u_ether.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 3c5a6f6ac341..6e4ff64532c2 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -1032,7 +1032,7 @@ int gether_set_ifname(struct net_device *net, const char *name, int len)
 	if (!p || p[1] != 'd' || strchr(p + 2, '%'))
 		return -EINVAL;
 
-	strncpy(net->name, tmp, sizeof(net->name));
+	strscpy(net->name, tmp);
 	dev->ifname_set = true;
 
 	return 0;

---
base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
change-id: 20240318-strncpy-drivers-usb-gadget-function-u_ether-c-125ed8336ca5

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

Re: [PATCH] usb: gadget: u_ether: replace deprecated strncpy with strscpy

[Kees Cook]

On Mon, Mar 18, 2024 at 11:10:34PM +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.
> 
> Let's use the new 2-argument strscpy() as this guarantees
> NUL-termination on the destination buffer and also uses the destination
> buffer's size to bound the operation.
> 
> 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>

Looks correct. Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook