Re: [PATCH] Revert "HID: uhid: use strlcpy() instead of strncpy()"

[David Herrmann]

Hi

On Thu, Nov 15, 2018 at 12:09 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Wed, Nov 14, 2018 at 9:40 AM, Laura Abbott <labbott@xxxxxxxxxx> wrote:
[...]
> > Can we switch to strscpy instead? This will quiet gcc and avoid the
> > issues with strlcpy.
>
> Yes please: it looks like these strings are expected to be NUL
> terminated, so strscpy() without the "- 1" and min() logic would be
> the correct solution here.

"the correct solution"? To my knowledge the original code was correct
as well. Am I missing something?

>                            If @hid is already zero, then this would
> just be:
>
>        strscpy(hid->name, ev->u.create2.name, sizeof(hid->name));
>        strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
>        strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
>
> If they are NOT NUL terminated, then keep using strncpy() but mark the
> fields in the struct with the __nonstring attribute.

They are supposed to be NUL terminated, but for compatibility reasons
we allow them to be not. So I don't think your proposal is safe.

Thanks
David