[PATCH] usb: gadget: mv_u3d: replace deprecated strncpy with strscpy

[PATCH] usb: gadget: mv_u3d: 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 opt for the new 2-argument version of strscpy() which guarantees
NUL-termination on the destination buffer and simplifies snytax. The
NUL-padding behavior that strncpy() provides is not required as u3d->eps
is already zero-allocated:
|	u3d->eps = kzalloc(size, GFP_KERNEL);

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/udc/mv_u3d_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/udc/mv_u3d_core.c b/drivers/usb/gadget/udc/mv_u3d_core.c
index 2a421f0ff931..e1dd5cf25d08 100644
--- a/drivers/usb/gadget/udc/mv_u3d_core.c
+++ b/drivers/usb/gadget/udc/mv_u3d_core.c
@@ -1307,7 +1307,7 @@ static int mv_u3d_eps_init(struct mv_u3d *u3d)
 	/* initialize ep0, ep0 in/out use eps[1] */
 	ep = &u3d->eps[1];
 	ep->u3d = u3d;
-	strncpy(ep->name, "ep0", sizeof(ep->name));
+	strscpy(ep->name, "ep0");
 	ep->ep.name = ep->name;
 	ep->ep.ops = &mv_u3d_ep_ops;
 	ep->wedge = 0;
@@ -1337,7 +1337,7 @@ static int mv_u3d_eps_init(struct mv_u3d *u3d)
 			ep->ep.caps.dir_out = true;
 		}
 		ep->u3d = u3d;
-		strncpy(ep->name, name, sizeof(ep->name));
+		strscpy(ep->name, name);
 		ep->ep.name = ep->name;
 
 		ep->ep.caps.type_iso = true;

---
base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400
change-id: 20240318-strncpy-drivers-usb-gadget-udc-mv_u3d_core-c-50ea7422311c

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

Re: [PATCH] usb: gadget: mv_u3d: replace deprecated strncpy with strscpy

[Kees Cook]

On Mon, Mar 18, 2024 at 11:31:53PM +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 opt for the new 2-argument version of strscpy() which guarantees
> NUL-termination on the destination buffer and simplifies snytax. The
> NUL-padding behavior that strncpy() provides is not required as u3d->eps
> is already zero-allocated:
> |	u3d->eps = kzalloc(size, GFP_KERNEL);
> 
> 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>

Thanks!

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

-- 
Kees Cook