strscpy() vs strlcpy() and WARN_ONCE()

Hans Petter Selasky <hps@xxxxxxxxxxx> · Thu, 13 Dec 2018 13:37:14 +0100

commit c0decac19da3906d9b66291e57b7759489e1170f
Author: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Date:   Mon Sep 10 08:19:14 2018 -0400

    media: use strscpy() instead of strlcpy()

    The implementation of strscpy() is more robust and safer.

    That's now the recommended way to copy NUL terminated strings.

    Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
    Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>

Hi Mauro,

The following piece of the commit above I believe is wrong:

        if (descr)
-               WARN_ON(strlcpy(fmt->description, descr, sz) >= sz);
+               WARN_ON(strscpy(fmt->description, descr, sz) >= sz);
        fmt->flags = flags;

It should be:
		WARN_ON(strscpy(fmt->description, descr, sz) < 0);

I don't have time to make a full patch for this so please handle this 
issue for me. Thank you!

--HPS