Re: [PATCH 0/8] x86-64: Properly handle the length parameter [BZ# 24097]

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Jan 18, 2019 at 12:21 PM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> > On Fri, Jan 18, 2019 at 11:56 AM Florian Weimer <fweimer@redhat.com> wrote:
> >>
> >> * H. J. Lu:
> >>
> >> > On Fri, Jan 18, 2019 at 2:50 AM Florian Weimer <fweimer@redhat.com> wrote:
> >> >>
> >> >> * H. J. Lu:
> >> >>
> >> >> > On x32, the size_t parameter may be passed in the lower 32 bits of a
> >> >> > 64-bit register with the non-zero upper 32 bits.  The string/memory
> >> >> > functions written in assembly can only use the lower 32 bits of a
> >> >> > 64-bit register as length or must clear the upper 32 bits before using
> >> >> > the full 64-bit register for length.
> >> >> >
> >> >> > This pach fixes string/memory functions written in assembly for x32.
> >> >> > Tested on x86-64 and x32.  On x86-64, libc.so is the same with and
> >> >> > withou the fix.
> >> >>
> >> >> Can this bug result in buffer overflows?  Should we obtain a CVE
> >> >
> >> > Yes, definitely.
> >> >
> >> >> identifier?
> >> >>
> >> >
> >> > Yes, please.  Can you do that for me?
> >>
> >> Done, MITRE gave us CVE-2019-6488.  Please reference this in the
> >> ChangeLog and the commit message if you have not done so.  Please also
> >
> > Done.  I just regenerated and submitted the new patch set.
> >
> >> add short NEWS entry in the security section.  Thanks.
> >>
> >
> > I added:
> >
> >   CVE-2019-6488: On x32, the size_t parameter may be passed in the lower
> >   32 bits of a 64-bit register with the non-zero upper 32 bits.  When
> >   it happens, the string/memory functions written in assembly will cause
> >   buffer overflow if the full 64-bit register is used as the 32-bit
>
> I think we generally describe the faulty behavior in the past tense
> (“When this happen*ed*, the string/memory functions written in assembly
> *would* cause *a* buffer overflow if the full 64-bit register was
> used”).  The first sentence is still current behavior, so it's okay.

Like this?

  CVE-2019-6488: On x32, the size_t parameter may be passed in the lower
  32 bits of a 64-bit register with the non-zero upper 32 bits.  When
  it happened, the string/memory functions written in assembly would
  cause a buffer overflow if the full 64-bit register was used as the
  32-bit size_t value.  Reported by H.J. Lu.

> >   size_t value.  Reported by Florian Weimer.
>
> Huh.  Did I really report this?  When?

It was my misunderstanding.

-- 
H.J.