* [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
@ 2022-02-15 16:28 Noah Goldstein
2022-02-15 16:32 ` H.J. Lu
` (4 more replies)
0 siblings, 5 replies; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 16:28 UTC (permalink / raw)
To: libc-alpha
Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
are near the start of a page. To avoid having the result contimated by
these comparisons the `strcmp` variants would mask off these
comparisons. This was missing in the `strncmp` variants causing
the bug. This commit adds the masking to `strncmp` so that out of
range comparisons don't affect the result.
test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
well a full xcheck on x86_64 linux.
---
string/test-strncmp.c | 24 ++++++++++++++++++++++++
sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
3 files changed, 26 insertions(+)
diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index 831cb77893..501055de0c 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -423,6 +423,29 @@ check3 (void)
}
}
+
+static void
+check4 (void)
+{
+ /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
+ the end of the page. 2) For there to be no mismatch/null byte before the
+ first page cross. 3) For length (`n`) to be large enough for one string to
+ cross the page. And 4) for there to be either mismatch/null bytes before
+ the start of the strings. */
+
+ size_t size = 10;
+ CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
+ CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
+ int exp_result;
+
+ STRCPY (s1, L ("tst-tlsmod%"));
+ STRCPY (s2, L ("tst-tls-manydynamic73mod"));
+ exp_result = SIMPLE_STRNCMP (s1, s2, size);
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, s1, s2, size, exp_result);
+}
+
+
static void
check_overflow (void)
{
@@ -546,6 +569,7 @@ test_main (void)
check1 ();
check2 ();
check3 ();
+ check4 ();
printf ("%23s", "");
FOR_EACH_IMPL (impl, 0)
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 99e5349be8..07a5a2c889 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -661,6 +661,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx), %ecx
cmpl %ecx, %edx
diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index 6f42e3155a..56d8c118e4 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -689,6 +689,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
# ifdef USE_AS_WCSCMP
--
2.25.1
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
@ 2022-02-15 16:32 ` H.J. Lu
2022-02-15 16:42 ` Noah Goldstein
2022-02-15 16:42 ` [PATCH v2] " Noah Goldstein
` (3 subsequent siblings)
4 siblings, 1 reply; 15+ messages in thread
From: H.J. Lu @ 2022-02-15 16:32 UTC (permalink / raw)
To: Noah Goldstein; +Cc: GNU C Library, Carlos O'Donell
On Tue, Feb 15, 2022 at 8:28 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> are near the start of a page. To avoid having the result contimated by
> these comparisons the `strcmp` variants would mask off these
> comparisons. This was missing in the `strncmp` variants causing
> the bug. This commit adds the masking to `strncmp` so that out of
> range comparisons don't affect the result.
>
> test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> well a full xcheck on x86_64 linux.
> ---
> string/test-strncmp.c | 24 ++++++++++++++++++++++++
> sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> 3 files changed, 26 insertions(+)
>
> diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> index 831cb77893..501055de0c 100644
> --- a/string/test-strncmp.c
> +++ b/string/test-strncmp.c
> @@ -423,6 +423,29 @@ check3 (void)
> }
> }
>
> +
Remove the extra blank line.
> +static void
> +check4 (void)
> +{
> + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> + the end of the page. 2) For there to be no mismatch/null byte before the
> + first page cross. 3) For length (`n`) to be large enough for one string to
> + cross the page. And 4) for there to be either mismatch/null bytes before
> + the start of the strings. */
> +
> + size_t size = 10;
> + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
> + int exp_result;
> +
> + STRCPY (s1, L ("tst-tlsmod%"));
> + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> + FOR_EACH_IMPL (impl, 0)
> + check_result (impl, s1, s2, size, exp_result);
> +}
> +
> +
Remove the extra blank line.
> static void
> check_overflow (void)
> {
> @@ -546,6 +569,7 @@ test_main (void)
> check1 ();
> check2 ();
> check3 ();
> + check4 ();
>
> printf ("%23s", "");
> FOR_EACH_IMPL (impl, 0)
> diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> index 99e5349be8..07a5a2c889 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> @@ -661,6 +661,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx), %ecx
> cmpl %ecx, %edx
> diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> index 6f42e3155a..56d8c118e4 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> @@ -689,6 +689,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> # ifdef USE_AS_WCSCMP
> --
> 2.25.1
>
OK for master and 2.35 backport with the extra blank line removal.
Thanks.
--
H.J.
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH v2] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
2022-02-15 16:32 ` H.J. Lu
@ 2022-02-15 16:42 ` Noah Goldstein
2022-02-15 16:45 ` H.J. Lu
2022-02-15 16:48 ` [PATCH v1] " Andreas Schwab
` (2 subsequent siblings)
4 siblings, 1 reply; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 16:42 UTC (permalink / raw)
To: libc-alpha
Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
are near the start of a page. To avoid having the result contimated by
these comparisons the `strcmp` variants would mask off these
comparisons. This was missing in the `strncmp` variants causing
the bug. This commit adds the masking to `strncmp` so that out of
range comparisons don't affect the result.
test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
well a full xcheck on x86_64 linux.
---
string/test-strncmp.c | 22 ++++++++++++++++++++++
sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
3 files changed, 24 insertions(+)
diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index 831cb77893..090b61316c 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -423,6 +423,27 @@ check3 (void)
}
}
+static void
+check4 (void)
+{
+ /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
+ the end of the page. 2) For there to be no mismatch/null byte before the
+ first page cross. 3) For length (`n`) to be large enough for one string to
+ cross the page. And 4) for there to be either mismatch/null bytes before
+ the start of the strings. */
+
+ size_t size = 10;
+ CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
+ CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
+ int exp_result;
+
+ STRCPY (s1, L ("tst-tlsmod%"));
+ STRCPY (s2, L ("tst-tls-manydynamic73mod"));
+ exp_result = SIMPLE_STRNCMP (s1, s2, size);
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, s1, s2, size, exp_result);
+}
+
static void
check_overflow (void)
{
@@ -546,6 +567,7 @@ test_main (void)
check1 ();
check2 ();
check3 ();
+ check4 ();
printf ("%23s", "");
FOR_EACH_IMPL (impl, 0)
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 99e5349be8..07a5a2c889 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -661,6 +661,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx), %ecx
cmpl %ecx, %edx
diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index 6f42e3155a..56d8c118e4 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -689,6 +689,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
# ifdef USE_AS_WCSCMP
--
2.25.1
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:32 ` H.J. Lu
@ 2022-02-15 16:42 ` Noah Goldstein
2022-02-15 16:44 ` H.J. Lu
0 siblings, 1 reply; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 16:42 UTC (permalink / raw)
To: H.J. Lu; +Cc: GNU C Library, Carlos O'Donell
On Tue, Feb 15, 2022 at 10:32 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Feb 15, 2022 at 8:28 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> > are near the start of a page. To avoid having the result contimated by
> > these comparisons the `strcmp` variants would mask off these
> > comparisons. This was missing in the `strncmp` variants causing
> > the bug. This commit adds the masking to `strncmp` so that out of
> > range comparisons don't affect the result.
> >
> > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> > well a full xcheck on x86_64 linux.
> > ---
> > string/test-strncmp.c | 24 ++++++++++++++++++++++++
> > sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> > sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> > 3 files changed, 26 insertions(+)
> >
> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> > index 831cb77893..501055de0c 100644
> > --- a/string/test-strncmp.c
> > +++ b/string/test-strncmp.c
> > @@ -423,6 +423,29 @@ check3 (void)
> > }
> > }
> >
> > +
>
> Remove the extra blank line.
Done in V2.
>
> > +static void
> > +check4 (void)
> > +{
> > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> > + the end of the page. 2) For there to be no mismatch/null byte before the
> > + first page cross. 3) For length (`n`) to be large enough for one string to
> > + cross the page. And 4) for there to be either mismatch/null bytes before
> > + the start of the strings. */
> > +
> > + size_t size = 10;
> > + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> > + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
> > + int exp_result;
> > +
> > + STRCPY (s1, L ("tst-tlsmod%"));
> > + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> > + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> > + FOR_EACH_IMPL (impl, 0)
> > + check_result (impl, s1, s2, size, exp_result);
> > +}
> > +
> > +
>
> Remove the extra blank line.
Done in V2.
>
> > static void
> > check_overflow (void)
> > {
> > @@ -546,6 +569,7 @@ test_main (void)
> > check1 ();
> > check2 ();
> > check3 ();
> > + check4 ();
> >
> > printf ("%23s", "");
> > FOR_EACH_IMPL (impl, 0)
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > index 99e5349be8..07a5a2c889 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > @@ -661,6 +661,7 @@ L(ret8):
> > # ifdef USE_AS_STRNCMP
> > .p2align 4,, 10
> > L(return_page_cross_end_check):
> > + andl %r10d, %ecx
> > tzcntl %ecx, %ecx
> > leal -VEC_SIZE(%rax, %rcx), %ecx
> > cmpl %ecx, %edx
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > index 6f42e3155a..56d8c118e4 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > @@ -689,6 +689,7 @@ L(ret8):
> > # ifdef USE_AS_STRNCMP
> > .p2align 4,, 10
> > L(return_page_cross_end_check):
> > + andl %r10d, %ecx
> > tzcntl %ecx, %ecx
> > leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> > # ifdef USE_AS_WCSCMP
> > --
> > 2.25.1
> >
>
> OK for master and 2.35 backport with the extra blank line removal.
Bug isn't present in 2.35. We had the foresight to wait until 2.36 to
push this.
>
> Thanks.
>
> --
> H.J.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:42 ` Noah Goldstein
@ 2022-02-15 16:44 ` H.J. Lu
0 siblings, 0 replies; 15+ messages in thread
From: H.J. Lu @ 2022-02-15 16:44 UTC (permalink / raw)
To: Noah Goldstein; +Cc: GNU C Library, Carlos O'Donell
On Tue, Feb 15, 2022 at 8:43 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Tue, Feb 15, 2022 at 10:32 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Tue, Feb 15, 2022 at 8:28 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> > > are near the start of a page. To avoid having the result contimated by
> > > these comparisons the `strcmp` variants would mask off these
> > > comparisons. This was missing in the `strncmp` variants causing
> > > the bug. This commit adds the masking to `strncmp` so that out of
> > > range comparisons don't affect the result.
> > >
> > > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> > > well a full xcheck on x86_64 linux.
> > > ---
> > > string/test-strncmp.c | 24 ++++++++++++++++++++++++
> > > sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> > > sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> > > 3 files changed, 26 insertions(+)
> > >
> > > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> > > index 831cb77893..501055de0c 100644
> > > --- a/string/test-strncmp.c
> > > +++ b/string/test-strncmp.c
> > > @@ -423,6 +423,29 @@ check3 (void)
> > > }
> > > }
> > >
> > > +
> >
> > Remove the extra blank line.
>
> Done in V2.
> >
> > > +static void
> > > +check4 (void)
> > > +{
> > > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> > > + the end of the page. 2) For there to be no mismatch/null byte before the
> > > + first page cross. 3) For length (`n`) to be large enough for one string to
> > > + cross the page. And 4) for there to be either mismatch/null bytes before
> > > + the start of the strings. */
> > > +
> > > + size_t size = 10;
> > > + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> > > + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
> > > + int exp_result;
> > > +
> > > + STRCPY (s1, L ("tst-tlsmod%"));
> > > + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> > > + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> > > + FOR_EACH_IMPL (impl, 0)
> > > + check_result (impl, s1, s2, size, exp_result);
> > > +}
> > > +
> > > +
> >
> > Remove the extra blank line.
>
> Done in V2.
> >
> > > static void
> > > check_overflow (void)
> > > {
> > > @@ -546,6 +569,7 @@ test_main (void)
> > > check1 ();
> > > check2 ();
> > > check3 ();
> > > + check4 ();
> > >
> > > printf ("%23s", "");
> > > FOR_EACH_IMPL (impl, 0)
> > > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > index 99e5349be8..07a5a2c889 100644
> > > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > @@ -661,6 +661,7 @@ L(ret8):
> > > # ifdef USE_AS_STRNCMP
> > > .p2align 4,, 10
> > > L(return_page_cross_end_check):
> > > + andl %r10d, %ecx
> > > tzcntl %ecx, %ecx
> > > leal -VEC_SIZE(%rax, %rcx), %ecx
> > > cmpl %ecx, %edx
> > > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > index 6f42e3155a..56d8c118e4 100644
> > > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > @@ -689,6 +689,7 @@ L(ret8):
> > > # ifdef USE_AS_STRNCMP
> > > .p2align 4,, 10
> > > L(return_page_cross_end_check):
> > > + andl %r10d, %ecx
> > > tzcntl %ecx, %ecx
> > > leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> > > # ifdef USE_AS_WCSCMP
> > > --
> > > 2.25.1
> > >
> >
> > OK for master and 2.35 backport with the extra blank line removal.
>
> Bug isn't present in 2.35. We had the foresight to wait until 2.36 to
> push this.
Glad to hear it :-).
--
H.J.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v2] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:42 ` [PATCH v2] " Noah Goldstein
@ 2022-02-15 16:45 ` H.J. Lu
0 siblings, 0 replies; 15+ messages in thread
From: H.J. Lu @ 2022-02-15 16:45 UTC (permalink / raw)
To: Noah Goldstein; +Cc: GNU C Library, Carlos O'Donell
On Tue, Feb 15, 2022 at 8:42 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> are near the start of a page. To avoid having the result contimated by
> these comparisons the `strcmp` variants would mask off these
> comparisons. This was missing in the `strncmp` variants causing
> the bug. This commit adds the masking to `strncmp` so that out of
> range comparisons don't affect the result.
>
> test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> well a full xcheck on x86_64 linux.
> ---
> string/test-strncmp.c | 22 ++++++++++++++++++++++
> sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> 3 files changed, 24 insertions(+)
>
> diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> index 831cb77893..090b61316c 100644
> --- a/string/test-strncmp.c
> +++ b/string/test-strncmp.c
> @@ -423,6 +423,27 @@ check3 (void)
> }
> }
>
> +static void
> +check4 (void)
> +{
> + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> + the end of the page. 2) For there to be no mismatch/null byte before the
> + first page cross. 3) For length (`n`) to be large enough for one string to
> + cross the page. And 4) for there to be either mismatch/null bytes before
> + the start of the strings. */
> +
> + size_t size = 10;
> + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
> + int exp_result;
> +
> + STRCPY (s1, L ("tst-tlsmod%"));
> + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> + FOR_EACH_IMPL (impl, 0)
> + check_result (impl, s1, s2, size, exp_result);
> +}
> +
> static void
> check_overflow (void)
> {
> @@ -546,6 +567,7 @@ test_main (void)
> check1 ();
> check2 ();
> check3 ();
> + check4 ();
>
> printf ("%23s", "");
> FOR_EACH_IMPL (impl, 0)
> diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> index 99e5349be8..07a5a2c889 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> @@ -661,6 +661,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx), %ecx
> cmpl %ecx, %edx
> diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> index 6f42e3155a..56d8c118e4 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> @@ -689,6 +689,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> # ifdef USE_AS_WCSCMP
> --
> 2.25.1
>
LGTM.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Thanks.
--
H.J.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
2022-02-15 16:32 ` H.J. Lu
2022-02-15 16:42 ` [PATCH v2] " Noah Goldstein
@ 2022-02-15 16:48 ` Andreas Schwab
2022-02-15 16:49 ` Noah Goldstein
2022-02-15 17:23 ` [PATCH v3] " Noah Goldstein
2022-02-16 2:27 ` [PATCH v4] " Noah Goldstein
4 siblings, 1 reply; 15+ messages in thread
From: Andreas Schwab @ 2022-02-15 16:48 UTC (permalink / raw)
To: Noah Goldstein via Libc-alpha
On Feb 15 2022, Noah Goldstein via Libc-alpha wrote:
> diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> index 831cb77893..501055de0c 100644
> --- a/string/test-strncmp.c
> +++ b/string/test-strncmp.c
> @@ -423,6 +423,29 @@ check3 (void)
> }
> }
>
> +
> +static void
> +check4 (void)
> +{
> + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> + the end of the page. 2) For there to be no mismatch/null byte before the
> + first page cross. 3) For length (`n`) to be large enough for one string to
> + cross the page. And 4) for there to be either mismatch/null bytes before
> + the start of the strings. */
> +
> + size_t size = 10;
> + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
s/&/-/
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:48 ` [PATCH v1] " Andreas Schwab
@ 2022-02-15 16:49 ` Noah Goldstein
2022-02-15 17:04 ` Andreas Schwab
0 siblings, 1 reply; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 16:49 UTC (permalink / raw)
To: Andreas Schwab; +Cc: Noah Goldstein via Libc-alpha
On Tue, Feb 15, 2022 at 10:48 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>
> On Feb 15 2022, Noah Goldstein via Libc-alpha wrote:
>
> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> > index 831cb77893..501055de0c 100644
> > --- a/string/test-strncmp.c
> > +++ b/string/test-strncmp.c
> > @@ -423,6 +423,29 @@ check3 (void)
> > }
> > }
> >
> > +
> > +static void
> > +check4 (void)
> > +{
> > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> > + the end of the page. 2) For there to be no mismatch/null byte before the
> > + first page cross. 3) For length (`n`) to be large enough for one string to
> > + cross the page. And 4) for there to be either mismatch/null bytes before
> > + the start of the strings. */
> > +
> > + size_t size = 10;
> > + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> > + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
>
> s/&/-/
?
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
> "And now for something completely different."
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:49 ` Noah Goldstein
@ 2022-02-15 17:04 ` Andreas Schwab
2022-02-15 17:24 ` Noah Goldstein
0 siblings, 1 reply; 15+ messages in thread
From: Andreas Schwab @ 2022-02-15 17:04 UTC (permalink / raw)
To: Noah Goldstein; +Cc: Noah Goldstein via Libc-alpha
On Feb 15 2022, Noah Goldstein wrote:
> On Tue, Feb 15, 2022 at 10:48 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>>
>> On Feb 15 2022, Noah Goldstein via Libc-alpha wrote:
>>
>> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
>> > index 831cb77893..501055de0c 100644
>> > --- a/string/test-strncmp.c
>> > +++ b/string/test-strncmp.c
>> > @@ -423,6 +423,29 @@ check3 (void)
>> > }
>> > }
>> >
>> > +
>> > +static void
>> > +check4 (void)
>> > +{
>> > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
>> > + the end of the page. 2) For there to be no mismatch/null byte before the
>> > + first page cross. 3) For length (`n`) to be large enough for one string to
>> > + cross the page. And 4) for there to be either mismatch/null bytes before
>> > + the start of the strings. */
>> > +
>> > + size_t size = 10;
>> > + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
>> > + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
>>
>> s/&/-/
> ?
(0x1000 & 0xffa) == 0
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH v3] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
` (2 preceding siblings ...)
2022-02-15 16:48 ` [PATCH v1] " Andreas Schwab
@ 2022-02-15 17:23 ` Noah Goldstein
2022-02-15 18:11 ` Andreas Schwab
2022-02-16 2:27 ` [PATCH v4] " Noah Goldstein
4 siblings, 1 reply; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 17:23 UTC (permalink / raw)
To: libc-alpha
Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
are near the start of a page. To avoid having the result contimated by
these comparisons the `strcmp` variants would mask off these
comparisons. This was missing in the `strncmp` variants causing
the bug. This commit adds the masking to `strncmp` so that out of
range comparisons don't affect the result.
test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
well a full xcheck on x86_64 linux.
---
string/test-strncmp.c | 22 ++++++++++++++++++++++
sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
3 files changed, 24 insertions(+)
diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index 831cb77893..090b61316c 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -423,6 +423,27 @@ check3 (void)
}
}
+static void
+check4 (void)
+{
+ /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
+ the end of the page. 2) For there to be no mismatch/null byte before the
+ first page cross. 3) For length (`n`) to be large enough for one string to
+ cross the page. And 4) for there to be either mismatch/null bytes before
+ the start of the strings. */
+
+ size_t size = 10;
+ CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
+ CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
+ int exp_result;
+
+ STRCPY (s1, L ("tst-tlsmod%"));
+ STRCPY (s2, L ("tst-tls-manydynamic73mod"));
+ exp_result = SIMPLE_STRNCMP (s1, s2, size);
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, s1, s2, size, exp_result);
+}
+
static void
check_overflow (void)
{
@@ -546,6 +567,7 @@ test_main (void)
check1 ();
check2 ();
check3 ();
+ check4 ();
printf ("%23s", "");
FOR_EACH_IMPL (impl, 0)
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 99e5349be8..07a5a2c889 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -661,6 +661,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx), %ecx
cmpl %ecx, %edx
diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index 6f42e3155a..56d8c118e4 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -689,6 +689,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
# ifdef USE_AS_WCSCMP
--
2.25.1
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 17:04 ` Andreas Schwab
@ 2022-02-15 17:24 ` Noah Goldstein
0 siblings, 0 replies; 15+ messages in thread
From: Noah Goldstein @ 2022-02-15 17:24 UTC (permalink / raw)
To: Andreas Schwab; +Cc: Noah Goldstein via Libc-alpha
On Tue, Feb 15, 2022 at 11:04 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>
> On Feb 15 2022, Noah Goldstein wrote:
>
> > On Tue, Feb 15, 2022 at 10:48 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
> >>
> >> On Feb 15 2022, Noah Goldstein via Libc-alpha wrote:
> >>
> >> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> >> > index 831cb77893..501055de0c 100644
> >> > --- a/string/test-strncmp.c
> >> > +++ b/string/test-strncmp.c
> >> > @@ -423,6 +423,29 @@ check3 (void)
> >> > }
> >> > }
> >> >
> >> > +
> >> > +static void
> >> > +check4 (void)
> >> > +{
> >> > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> >> > + the end of the page. 2) For there to be no mismatch/null byte before the
> >> > + first page cross. 3) For length (`n`) to be large enough for one string to
> >> > + cross the page. And 4) for there to be either mismatch/null bytes before
> >> > + the start of the strings. */
> >> > +
> >> > + size_t size = 10;
> >> > + CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> >> > + CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
> >>
> >> s/&/-/
> > ?
>
> (0x1000 & 0xffa) == 0
:/
Fixed in V3.
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
> "And now for something completely different."
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v3] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 17:23 ` [PATCH v3] " Noah Goldstein
@ 2022-02-15 18:11 ` Andreas Schwab
0 siblings, 0 replies; 15+ messages in thread
From: Andreas Schwab @ 2022-02-15 18:11 UTC (permalink / raw)
To: Noah Goldstein via Libc-alpha
Identical to v2.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 15+ messages in thread
* [PATCH v4] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
` (3 preceding siblings ...)
2022-02-15 17:23 ` [PATCH v3] " Noah Goldstein
@ 2022-02-16 2:27 ` Noah Goldstein
2022-02-16 2:28 ` H.J. Lu
4 siblings, 1 reply; 15+ messages in thread
From: Noah Goldstein @ 2022-02-16 2:27 UTC (permalink / raw)
To: libc-alpha
Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
are near the start of a page. To avoid having the result contimated by
these comparisons the `strcmp` variants would mask off these
comparisons. This was missing in the `strncmp` variants causing
the bug. This commit adds the masking to `strncmp` so that out of
range comparisons don't affect the result.
test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
well a full xcheck on x86_64 linux.
---
string/test-strncmp.c | 23 +++++++++++++++++++++++
sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
3 files changed, 25 insertions(+)
diff --git a/string/test-strncmp.c b/string/test-strncmp.c
index 831cb77893..df7cea4068 100644
--- a/string/test-strncmp.c
+++ b/string/test-strncmp.c
@@ -423,6 +423,28 @@ check3 (void)
}
}
+static void
+check4 (void)
+{
+ /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
+ the end of the page. 2) For there to be no mismatch/null byte before the
+ first page cross. 3) For length (`n`) to be large enough for one string to
+ cross the page. And 4) for there to be either mismatch/null bytes before
+ the start of the strings. */
+
+ size_t size = 10;
+ size_t addr_mask = (getpagesize () - 1) ^ (sizeof (CHAR) - 1);
+ CHAR *s1 = (CHAR *)(buf1 + (addr_mask & 0xffa));
+ CHAR *s2 = (CHAR *)(buf2 + (addr_mask & 0xfed));
+ int exp_result;
+
+ STRCPY (s1, L ("tst-tlsmod%"));
+ STRCPY (s2, L ("tst-tls-manydynamic73mod"));
+ exp_result = SIMPLE_STRNCMP (s1, s2, size);
+ FOR_EACH_IMPL (impl, 0)
+ check_result (impl, s1, s2, size, exp_result);
+}
+
static void
check_overflow (void)
{
@@ -546,6 +568,7 @@ test_main (void)
check1 ();
check2 ();
check3 ();
+ check4 ();
printf ("%23s", "");
FOR_EACH_IMPL (impl, 0)
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 99e5349be8..07a5a2c889 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -661,6 +661,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx), %ecx
cmpl %ecx, %edx
diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index 6f42e3155a..56d8c118e4 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -689,6 +689,7 @@ L(ret8):
# ifdef USE_AS_STRNCMP
.p2align 4,, 10
L(return_page_cross_end_check):
+ andl %r10d, %ecx
tzcntl %ecx, %ecx
leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
# ifdef USE_AS_WCSCMP
--
2.25.1
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v4] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-16 2:27 ` [PATCH v4] " Noah Goldstein
@ 2022-02-16 2:28 ` H.J. Lu
2022-05-04 6:02 ` Sunil Pandey
0 siblings, 1 reply; 15+ messages in thread
From: H.J. Lu @ 2022-02-16 2:28 UTC (permalink / raw)
To: Noah Goldstein; +Cc: GNU C Library, Carlos O'Donell
On Tue, Feb 15, 2022 at 6:27 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> are near the start of a page. To avoid having the result contimated by
> these comparisons the `strcmp` variants would mask off these
> comparisons. This was missing in the `strncmp` variants causing
> the bug. This commit adds the masking to `strncmp` so that out of
> range comparisons don't affect the result.
>
> test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> well a full xcheck on x86_64 linux.
> ---
> string/test-strncmp.c | 23 +++++++++++++++++++++++
> sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> 3 files changed, 25 insertions(+)
>
> diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> index 831cb77893..df7cea4068 100644
> --- a/string/test-strncmp.c
> +++ b/string/test-strncmp.c
> @@ -423,6 +423,28 @@ check3 (void)
> }
> }
>
> +static void
> +check4 (void)
> +{
> + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> + the end of the page. 2) For there to be no mismatch/null byte before the
> + first page cross. 3) For length (`n`) to be large enough for one string to
> + cross the page. And 4) for there to be either mismatch/null bytes before
> + the start of the strings. */
> +
> + size_t size = 10;
> + size_t addr_mask = (getpagesize () - 1) ^ (sizeof (CHAR) - 1);
> + CHAR *s1 = (CHAR *)(buf1 + (addr_mask & 0xffa));
> + CHAR *s2 = (CHAR *)(buf2 + (addr_mask & 0xfed));
> + int exp_result;
> +
> + STRCPY (s1, L ("tst-tlsmod%"));
> + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> + FOR_EACH_IMPL (impl, 0)
> + check_result (impl, s1, s2, size, exp_result);
> +}
> +
> static void
> check_overflow (void)
> {
> @@ -546,6 +568,7 @@ test_main (void)
> check1 ();
> check2 ();
> check3 ();
> + check4 ();
>
> printf ("%23s", "");
> FOR_EACH_IMPL (impl, 0)
> diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> index 99e5349be8..07a5a2c889 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> @@ -661,6 +661,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx), %ecx
> cmpl %ecx, %edx
> diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> index 6f42e3155a..56d8c118e4 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> @@ -689,6 +689,7 @@ L(ret8):
> # ifdef USE_AS_STRNCMP
> .p2align 4,, 10
> L(return_page_cross_end_check):
> + andl %r10d, %ecx
> tzcntl %ecx, %ecx
> leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> # ifdef USE_AS_WCSCMP
> --
> 2.25.1
>
LGTM.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Thanks.
--
H.J.
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [PATCH v4] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]
2022-02-16 2:28 ` H.J. Lu
@ 2022-05-04 6:02 ` Sunil Pandey
0 siblings, 0 replies; 15+ messages in thread
From: Sunil Pandey @ 2022-05-04 6:02 UTC (permalink / raw)
To: H.J. Lu, Libc-stable Mailing List; +Cc: Noah Goldstein, GNU C Library
On Tue, Feb 15, 2022 at 6:29 PM H.J. Lu via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Tue, Feb 15, 2022 at 6:27 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > Logic can read before the start of `s1` / `s2` if both `s1` and `s2`
> > are near the start of a page. To avoid having the result contimated by
> > these comparisons the `strcmp` variants would mask off these
> > comparisons. This was missing in the `strncmp` variants causing
> > the bug. This commit adds the masking to `strncmp` so that out of
> > range comparisons don't affect the result.
> >
> > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass as
> > well a full xcheck on x86_64 linux.
> > ---
> > string/test-strncmp.c | 23 +++++++++++++++++++++++
> > sysdeps/x86_64/multiarch/strcmp-avx2.S | 1 +
> > sysdeps/x86_64/multiarch/strcmp-evex.S | 1 +
> > 3 files changed, 25 insertions(+)
> >
> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> > index 831cb77893..df7cea4068 100644
> > --- a/string/test-strncmp.c
> > +++ b/string/test-strncmp.c
> > @@ -423,6 +423,28 @@ check3 (void)
> > }
> > }
> >
> > +static void
> > +check4 (void)
> > +{
> > + /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> > + the end of the page. 2) For there to be no mismatch/null byte before the
> > + first page cross. 3) For length (`n`) to be large enough for one string to
> > + cross the page. And 4) for there to be either mismatch/null bytes before
> > + the start of the strings. */
> > +
> > + size_t size = 10;
> > + size_t addr_mask = (getpagesize () - 1) ^ (sizeof (CHAR) - 1);
> > + CHAR *s1 = (CHAR *)(buf1 + (addr_mask & 0xffa));
> > + CHAR *s2 = (CHAR *)(buf2 + (addr_mask & 0xfed));
> > + int exp_result;
> > +
> > + STRCPY (s1, L ("tst-tlsmod%"));
> > + STRCPY (s2, L ("tst-tls-manydynamic73mod"));
> > + exp_result = SIMPLE_STRNCMP (s1, s2, size);
> > + FOR_EACH_IMPL (impl, 0)
> > + check_result (impl, s1, s2, size, exp_result);
> > +}
> > +
> > static void
> > check_overflow (void)
> > {
> > @@ -546,6 +568,7 @@ test_main (void)
> > check1 ();
> > check2 ();
> > check3 ();
> > + check4 ();
> >
> > printf ("%23s", "");
> > FOR_EACH_IMPL (impl, 0)
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > index 99e5349be8..07a5a2c889 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > @@ -661,6 +661,7 @@ L(ret8):
> > # ifdef USE_AS_STRNCMP
> > .p2align 4,, 10
> > L(return_page_cross_end_check):
> > + andl %r10d, %ecx
> > tzcntl %ecx, %ecx
> > leal -VEC_SIZE(%rax, %rcx), %ecx
> > cmpl %ecx, %edx
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > index 6f42e3155a..56d8c118e4 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > @@ -689,6 +689,7 @@ L(ret8):
> > # ifdef USE_AS_STRNCMP
> > .p2align 4,, 10
> > L(return_page_cross_end_check):
> > + andl %r10d, %ecx
> > tzcntl %ecx, %ecx
> > leal -VEC_SIZE(%rax, %rcx, SIZE_OF_CHAR), %ecx
> > # ifdef USE_AS_WCSCMP
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.
I would like to backport this patch to release branches.
Any comments or objections?
--Sunil
^ permalink raw reply [flat|nested] 15+ messages in thread
end of thread, other threads:[~2022-05-04 6:03 UTC | newest]
Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-15 16:28 [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895] Noah Goldstein
2022-02-15 16:32 ` H.J. Lu
2022-02-15 16:42 ` Noah Goldstein
2022-02-15 16:44 ` H.J. Lu
2022-02-15 16:42 ` [PATCH v2] " Noah Goldstein
2022-02-15 16:45 ` H.J. Lu
2022-02-15 16:48 ` [PATCH v1] " Andreas Schwab
2022-02-15 16:49 ` Noah Goldstein
2022-02-15 17:04 ` Andreas Schwab
2022-02-15 17:24 ` Noah Goldstein
2022-02-15 17:23 ` [PATCH v3] " Noah Goldstein
2022-02-15 18:11 ` Andreas Schwab
2022-02-16 2:27 ` [PATCH v4] " Noah Goldstein
2022-02-16 2:28 ` H.J. Lu
2022-05-04 6:02 ` Sunil Pandey
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