Re: [PATCH] usb: gadget: function: printer: Replace strlcpy with strscpy

[Azeem Shaikh]

On Wed, Jun 14, 2023 at 1:51 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> On Wed, Jun 14, 2023 at 10:12:14AM -0400, Azeem Shaikh wrote:
> > On Tue, Jun 13, 2023 at 3:30 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> > >
> > > On Tue, Jun 13, 2023 at 12:43:41AM +0000, Azeem Shaikh wrote:
> > [...]
> > > > -     result = strlcpy(page, opts->pnp_string, PAGE_SIZE);
> > > > -     if (result >= PAGE_SIZE) {
> > > > +     result = strscpy(page, opts->pnp_string, PAGE_SIZE);
> > > > +     if (result == -E2BIG) {
> > >
> > > I think "< 1" might be a better test here.
> >
> > Curious, why "< 1" instead of "< 0"?
> >
> > > >               result = PAGE_SIZE;
> > > >       } else if (page[result - 1] != '\n' && result + 1 < PAGE_SIZE) {
>
> It's for this case above where "result" may be used in an array index,
> and if it's 0 or less, there will be a negative array index (due to the "-
> 1"). So, here, it needs to be "< 1" instead of the more traditional "< 0".
>

Makes sense. Sent out a v2.