From: Sunil Pandey via Libc-alpha <libc-alpha@sourceware.org>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Libc-stable Mailing List <libc-stable@sourceware.org>,
Noah Goldstein <goldstein.w.n@gmail.com>,
libc-alpha@sourceware.org
Subject: Re: [PATCH v1] x86: Fix wcsnlen-avx2 page cross length comparison [BZ #29591]
Date: Wed, 23 Nov 2022 19:04:10 -0800 [thread overview]
Message-ID: <CAMAf5_doA_D3r1-J=7CTW1C=3eusTBBHbbnOLg3iu2scaesLyg@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOrBK2O690Kfg0wjsKzH6zcgao9agtJXOQnzSnAk-tCUAg@mail.gmail.com>
On Wed, Nov 23, 2022 at 4:23 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Nov 23, 2022 at 2:21 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
> >
> > On Wed, Sep 21, 2022 at 3:02 PM H.J. Lu via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> > >
> > > On Tue, Sep 20, 2022 at 5:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > > >
> > > > Previous implementation was adjusting length (rsi) to match
> > > > bytes (eax), but since there is no bound to length this can cause
> > > > overflow.
> > > >
> > > > Fix is to just convert the byte-count (eax) to length by dividing by
> > > > sizeof (wchar_t) before the comparison.
> > > >
> > > > Full check passes on x86-64 and build succeeds w/ and w/o multiarch.
> > > > ---
> > > > string/test-strnlen.c | 70 +++++++++++++++-----------
> > > > sysdeps/x86_64/multiarch/strlen-avx2.S | 7 +--
> > > > 2 files changed, 43 insertions(+), 34 deletions(-)
> > > >
> > > > diff --git a/string/test-strnlen.c b/string/test-strnlen.c
> > > > index 4a9375112a..5cbaf4b734 100644
> > > > --- a/string/test-strnlen.c
> > > > +++ b/string/test-strnlen.c
> > > > @@ -73,7 +73,7 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char)
> > > > {
> > > > size_t i;
> > > >
> > > > - align &= 63;
> > > > + align &= (getpagesize () / sizeof (CHAR) - 1);
> > > > if ((align + len) * sizeof (CHAR) >= page_size)
> > > > return;
> > > >
> > > > @@ -90,38 +90,50 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char)
> > > > static void
> > > > do_overflow_tests (void)
> > > > {
> > > > - size_t i, j, len;
> > > > + size_t i, j, al_idx, repeats, len;
> > > > const size_t one = 1;
> > > > uintptr_t buf_addr = (uintptr_t) buf1;
> > > > + const size_t alignments[] = { 0, 1, 7, 9, 31, 33, 63, 65, 95, 97, 127, 129 };
> > > >
> > > > - for (i = 0; i < 750; ++i)
> > > > + for (al_idx = 0; al_idx < sizeof (alignments) / sizeof (alignments[0]);
> > > > + al_idx++)
> > > > {
> > > > - do_test (1, i, SIZE_MAX, BIG_CHAR);
> > > > -
> > > > - do_test (0, i, SIZE_MAX - i, BIG_CHAR);
> > > > - do_test (0, i, i - buf_addr, BIG_CHAR);
> > > > - do_test (0, i, -buf_addr - i, BIG_CHAR);
> > > > - do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
> > > > - do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
> > > > -
> > > > - len = 0;
> > > > - for (j = 8 * sizeof(size_t) - 1; j ; --j)
> > > > - {
> > > > - len |= one << j;
> > > > - do_test (0, i, len - i, BIG_CHAR);
> > > > - do_test (0, i, len + i, BIG_CHAR);
> > > > - do_test (0, i, len - buf_addr - i, BIG_CHAR);
> > > > - do_test (0, i, len - buf_addr + i, BIG_CHAR);
> > > > -
> > > > - do_test (0, i, ~len - i, BIG_CHAR);
> > > > - do_test (0, i, ~len + i, BIG_CHAR);
> > > > - do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
> > > > - do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
> > > > -
> > > > - do_test (0, i, -buf_addr, BIG_CHAR);
> > > > - do_test (0, i, j - buf_addr, BIG_CHAR);
> > > > - do_test (0, i, -buf_addr - j, BIG_CHAR);
> > > > - }
> > > > + for (repeats = 0; repeats < 2; ++repeats)
> > > > + {
> > > > + size_t align = repeats ? (getpagesize () - alignments[al_idx])
> > > > + : alignments[al_idx];
> > > > + align /= sizeof (CHAR);
> > > > + for (i = 0; i < 750; ++i)
> > > > + {
> > > > + do_test (align, i, SIZE_MAX, BIG_CHAR);
> > > > +
> > > > + do_test (align, i, SIZE_MAX - i, BIG_CHAR);
> > > > + do_test (align, i, i - buf_addr, BIG_CHAR);
> > > > + do_test (align, i, -buf_addr - i, BIG_CHAR);
> > > > + do_test (align, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
> > > > + do_test (align, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
> > > > +
> > > > + len = 0;
> > > > + for (j = 8 * sizeof (size_t) - 1; j; --j)
> > > > + {
> > > > + len |= one << j;
> > > > + do_test (align, i, len, BIG_CHAR);
> > > > + do_test (align, i, len - i, BIG_CHAR);
> > > > + do_test (align, i, len + i, BIG_CHAR);
> > > > + do_test (align, i, len - buf_addr - i, BIG_CHAR);
> > > > + do_test (align, i, len - buf_addr + i, BIG_CHAR);
> > > > +
> > > > + do_test (align, i, ~len - i, BIG_CHAR);
> > > > + do_test (align, i, ~len + i, BIG_CHAR);
> > > > + do_test (align, i, ~len - buf_addr - i, BIG_CHAR);
> > > > + do_test (align, i, ~len - buf_addr + i, BIG_CHAR);
> > > > +
> > > > + do_test (align, i, -buf_addr, BIG_CHAR);
> > > > + do_test (align, i, j - buf_addr, BIG_CHAR);
> > > > + do_test (align, i, -buf_addr - j, BIG_CHAR);
> > > > + }
> > > > + }
> > > > + }
> > > > }
> > > > }
> > > >
> > > > diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S b/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > index 0593fb303b..b9b58ef599 100644
> > > > --- a/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > +++ b/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > @@ -544,14 +544,11 @@ L(return_vzeroupper):
> > > > L(cross_page_less_vec):
> > > > tzcntl %eax, %eax
> > > > # ifdef USE_AS_WCSLEN
> > > > - /* NB: Multiply length by 4 to get byte count. */
> > > > - sall $2, %esi
> > > > + /* NB: Divide by 4 to convert from byte-count to length. */
> > > > + shrl $2, %eax
> > > > # endif
> > > > cmpq %rax, %rsi
> > > > cmovb %esi, %eax
> > > > -# ifdef USE_AS_WCSLEN
> > > > - shrl $2, %eax
> > > > -# endif
> > > > VZEROUPPER_RETURN
> > > > # endif
> > > >
> > > > --
> > > > 2.34.1
> > > >
> > >
> > > LGTM.
> > >
> > > Thanks.
> > >
> > > --
> > > H.J.
> >
> > I would like to backport this patch to affected release branches from
> > 2.36 to 2.33.
> >
> > Any comments/suggestions or objections on this.
> >
>
> OK.
>
> Thanks.
>
>
> --
> H.J.
Just ran testing from 2.32 to 2.26. All of them have this issue.
Ok for 2.32 to 2.26 branches?
--Sunil
next prev parent reply other threads:[~2022-11-24 3:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 0:58 [PATCH v1] x86: Fix wcsnlen-avx2 page cross length comparison [BZ #29591] Noah Goldstein via Libc-alpha
2022-09-21 22:01 ` H.J. Lu via Libc-alpha
2022-11-23 22:20 ` Sunil Pandey via Libc-alpha
2022-11-24 0:22 ` H.J. Lu via Libc-alpha
2022-11-24 3:04 ` Sunil Pandey via Libc-alpha [this message]
2022-11-24 3:12 ` H.J. Lu via Libc-alpha
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