linux-kernel - Re: [PATCH v2] hex2bin: fix access beyond string end

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Message-ID: <CAHp75Vf=sEeoHwzb2RdVFsmZ_mWAyg2zdMKgtW9RQFM_bTMHPw@mail.gmail.com>
Date:   Wed, 27 Apr 2022 16:49:59 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andy@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        device-mapper development <dm-devel@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Snitzer <msnitzer@...hat.com>,
        Milan Broz <gmazyland@...il.com>
Subject: Re: [PATCH v2] hex2bin: fix access beyond string end

On Wed, Apr 27, 2022 at 4:10 PM Mikulas Patocka <mpatocka@...hat.com> wrote:
> On Wed, 27 Apr 2022, Andy Shevchenko wrote:
> > On Tue, Apr 26, 2022 at 5:29 PM Mikulas Patocka <mpatocka@...hat.com> wrote:
> > > On Tue, 26 Apr 2022, Andy Shevchenko wrote:
> > > > On Tue, Apr 26, 2022 at 08:07:44AM -0400, Mikulas Patocka wrote:
> > > > > On Tue, 26 Apr 2022, Andy Shevchenko wrote:
> > > > > > On Sun, Apr 24, 2022 at 10:48 PM Mikulas Patocka <mpatocka@...hat.com> wrote:
> >
> > ...
> >
> > > > Still shadows error codes.
> > > >
> > > > > +                   return -EINVAL;
> > > >
> > > > >                     return -EINVAL;
> > >
> > > What do you mean? What's wrong with "return -EINVAL"?
> >
> > The actual error code is returned by hex_to_bin(). What is the point
> > of shadowing it with the explicit value?
>
> hex_to_bin returns -1 on error, hex2bin returns -EINVAL on error.
>
> This is inconsistent and it may be fixed (after verifying all the
> hex_to_bin callers - a quick grep over the source shows that there is "if
> ((k = hex_to_bin(in_str[j--])) != -1)").
>
> But for the purpose of fixing this bug, we should preserve the behavior
> and return -1 and -EINVAL just like it was before.

This is clear now to me. So, by improving a commit message you may
make it clear to everybody who reads your change.

With the updated commit message,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

-- 
With Best Regards,
Andy Shevchenko