Re: [PATCH v5 04/16] include/grub/misc.h: Fix edge case in grub_uuidcasecmp()

[Daniel Kiper]

On Thu, Aug 31, 2023 at 05:32:14PM +0000, Vitaly Kuzmichev wrote:
> Hi Daniel,
>
> On Thu, 2023-08-31 at 19:09 +0200, Daniel Kiper wrote:
> > On Tue, Aug 22, 2023 at 11:39:12PM +0200, Vitaly Kuzmichev wrote:
> > > Fix comparison of two identical UUID strings ending with dash '-'.
> > >
> > > In this case grub_uuidcasecmp() passes through the null terminators
> > > and actual result depends on whatever garbage follows them.
> > >
> > > So break immediately when it reaches the end in any of the strings
> > > after a dash character '-'.
> > >
> > > Signed-off-by: Vitaly Kuzmichev <vitaly.kuzmichev@rtsoft.de>
> > > ---
> > >  include/grub/misc.h | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/include/grub/misc.h b/include/grub/misc.h
> > > index 1b35a167f..12fade5de 100644
> > > --- a/include/grub/misc.h
> > > +++ b/include/grub/misc.h
> > > @@ -264,7 +264,8 @@ grub_uuidcasecmp (const char *uuid1, const char
> > > *uuid2, grub_size_t n)
> > >        while ('-' == *uuid2)
> > >          ++uuid2;
> > >
> > > -      if (grub_tolower ((grub_uint8_t) *uuid1) != grub_tolower
> > > ((grub_uint8_t) *uuid2))
> > > +      if (!*uuid1 || !*uuid2 ||
> >
> > I prefer
> >
> >   if (*uuid1 != '\0' || *uuid2 != '\0' || ...
> >
> > ... if it is what you meant...
>
> Thank you for review.
>
> Actually, I meant equality to null terminator:
>   if (*uuid1 == '\0' || *uuid2 == '\0' || ...
>
> It should exit the loop when it finds one.

Nah, right. I inverted the conditions. Sorry...

> In the same function we have also a loop with similar condition without
> comparison operator as well:
>
>   while (*uuid1 && *uuid2 && --n)
>
> And also:
>   while ('-' == *uuid2)
>
> If I change my 'if' to the variant that you suggest, this would be a
> mix of three different coding styles in the same function.
>
> Should I fix them all to match your taste?

If you could do that it would be more than perfect. Of course in
separate patch...

Daniel