Re: [PATCH v2] test-strnlen.c: Check that strnlen won't go beyond the maximum length

Re: [PATCH v2] test-strnlen.c: Check that strnlen won't go beyond the maximum length

[H.J. Lu]

On Sat, Mar 27, 2021 at 11:34 AM Florian Weimer <fw@deneb.enyo.de> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> > From: "H.J. Lu" <hjl.tools@gmail.com>
> > Date: Sat, 27 Mar 2021 09:06:39 -0700
> > Subject: [PATCH v2] test-strnlen.c: Check that strnlen won't go beyond the
> >  maximum length
> >
> > Place strings ending at page boundary without the null byte.  If an
> > implementation goes beyond EXP_LEN, it will trigger the segfault.
> > ---
> >  string/test-strnlen.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/string/test-strnlen.c b/string/test-strnlen.c
> > index 0293acbc71..d70faa26ab 100644
> > --- a/string/test-strnlen.c
> > +++ b/string/test-strnlen.c
> > @@ -198,6 +198,35 @@ do_page_tests (void)
> >      }
> >  }
> >
> > +/* Tests meant to unveil fail on implementations that access bytes
> > +   beyond the maxium length.  */
> > +
> > +static void
> > +do_page_2_tests (void)
> > +{
> > +  size_t i, exp_len, offset;
> > +  size_t last_offset = page_size / sizeof (CHAR);
> > +
> > +  CHAR *s = (CHAR *) buf2;
> > +  MEMSET (s, 65, last_offset);
> > +
> > +  /* Place short strings ending at page boundary without the null
> > +     byte.  */
> > +  offset = last_offset;
> > +  for (i = 0; i < 128; i++)
> > +    {
> > +      /* Decrease offset to stress several sizes and alignments.  */
> > +      offset--;
> > +      exp_len = last_offset - offset;
> > +      FOR_EACH_IMPL (impl, 0)
> > +     {
> > +       /* If an implementation goes beyond EXP_LEN, it will trigger
> > +          the segfault.  */
> > +       do_one_test (impl, (CHAR *) (s + offset), exp_len, exp_len);
> > +     }
> > +    }
> > +}
>
> Thanks, looks good.  The comments and the commit message are much
> clearer now.

I am backporting this to release branches.

-- 
H.J.