[v2] x86: Fix strncat-avx2.S reading past length [BZ #30065]
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Context |
Check |
Description |
dj/TryBot-apply_patch |
success
|
Patch applied to master at the time it was sent
|
dj/TryBot-32bit |
success
|
Build for i686
|
Commit Message
Occurs when `src` has no null-term.
Two cases:
1) Zero-length check is doing:
```
test %rdx, %rdx
jl L(zero_len)
```
which doesn't actually check zero (was at some point `decq` and the
flag never got updated).
The fix is just make the flag `jle` i.e:
```
test %rdx, %rdx
jle L(zero_len)
```
2) Length check in page-cross case checking if we should continue is
doing:
```
cmpq %r8, %rdx
jb L(page_cross_small)
```
which means we will continue searching for null-term if length ends at
the end of a page and there was no null-term in `src`.
The fix is to make the flag:
```
cmpq %r8, %rdx
jbe L(page_cross_small)
```
---
string/test-strncat.c | 25 ++++++++++++++++++++++++-
sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
2 files changed, 26 insertions(+), 3 deletions(-)
Comments
On Tue, Jan 31, 2023 at 3:47 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> Occurs when `src` has no null-term.
>
> Two cases:
>
> 1) Zero-length check is doing:
> ```
> test %rdx, %rdx
> jl L(zero_len)
> ```
> which doesn't actually check zero (was at some point `decq` and the
> flag never got updated).
>
> The fix is just make the flag `jle` i.e:
> ```
> test %rdx, %rdx
> jle L(zero_len)
> ```
>
> 2) Length check in page-cross case checking if we should continue is
> doing:
> ```
> cmpq %r8, %rdx
> jb L(page_cross_small)
> ```
> which means we will continue searching for null-term if length ends at
> the end of a page and there was no null-term in `src`.
>
> The fix is to make the flag:
> ```
> cmpq %r8, %rdx
> jbe L(page_cross_small)
> ```
> ---
> string/test-strncat.c | 25 ++++++++++++++++++++++++-
> sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
> 2 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/string/test-strncat.c b/string/test-strncat.c
> index e03d329e1c..c0cde206ee 100644
> --- a/string/test-strncat.c
> +++ b/string/test-strncat.c
> @@ -28,6 +28,7 @@
> # define CHAR char
> # define UCHAR unsigned char
> # define SIMPLE_STRNCAT simple_strncat
> +# define STRNLEN strnlen
> # define STRLEN strlen
> # define MEMSET memset
> # define MEMCPY memcpy
> @@ -40,6 +41,7 @@
> # define CHAR wchar_t
> # define UCHAR wchar_t
> # define SIMPLE_STRNCAT simple_wcsncat
> +# define STRNLEN wcsnlen
> # define STRLEN wcslen
> # define MEMSET wmemset
> # define MEMCPY wmemcpy
> @@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> return;
> }
>
> - size_t len = STRLEN (src);
> + size_t len = STRNLEN (src, n);
> if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
> {
> error (0, 0, "Incorrect concatenation in function %s",
> @@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> }
> }
>
> +static void
> +do_test_src_no_nullterm_bz30065 (void)
> +{
> + /* NB: "src does not need to be null-terminated if it contains n or more
> + * bytes." */
> + CHAR *s1, *s2;
> + size_t bound = page_size / sizeof (CHAR);
> + s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
> + s2 = (CHAR *) buf2;
> + MEMSET (s1 - bound, -1, bound);
> + for (size_t n = 0; n < bound; ++n)
> + {
> + FOR_EACH_IMPL (impl, 0)
> + {
> + s2[0] = '\0';
> + do_one_test (impl, s2, s1 - n, n);
> + }
> + }
> +}
> +
> static void
> do_test (size_t align1, size_t align2, size_t len1, size_t len2,
> size_t n, int max_char)
> @@ -372,6 +394,7 @@ test_main (void)
>
> do_random_tests ();
> do_overflow_tests ();
> + do_test_src_no_nullterm_bz30065 ();
> return ret;
> }
>
> diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S
> index b380e8e11c..c2ff202238 100644
> --- a/sysdeps/x86_64/multiarch/strncat-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strncat-avx2.S
> @@ -66,7 +66,7 @@ ENTRY(STRNCAT)
> salq $2, %rdx
> # else
> test %rdx, %rdx
> - jl L(zero_len)
> + jle L(zero_len)
> # endif
> vpxor %VZERO_128, %VZERO_128, %VZERO_128
>
> @@ -387,7 +387,7 @@ L(page_cross):
> subl %esi, %r8d
> andl $(VEC_SIZE - 1), %r8d
> cmpq %r8, %rdx
> - jb L(page_cross_small)
> + jbe L(page_cross_small)
>
> /* Optimizing more aggressively for space as this is very cold
> code. This saves 2x cache lines. */
> --
> 2.34.1
>
LGTM.
Thanks.
On 1/31/23 18:46, Noah Goldstein via Libc-alpha wrote:
> Occurs when `src` has no null-term.
This has been pushed as b2c474f8de4c92bfe7435853a96805ec32d68dfa.
We are now in a hard freeze as I prepare to cut the release.
Please do not commit anything further.
If we find other issues we can backport to the release branch after testing.
I'm re-running testing with this patch included for x86_64 and i686.
> Two cases:
>
> 1) Zero-length check is doing:
> ```
> test %rdx, %rdx
> jl L(zero_len)
> ```
> which doesn't actually check zero (was at some point `decq` and the
> flag never got updated).
>
> The fix is just make the flag `jle` i.e:
> ```
> test %rdx, %rdx
> jle L(zero_len)
> ```
>
> 2) Length check in page-cross case checking if we should continue is
> doing:
> ```
> cmpq %r8, %rdx
> jb L(page_cross_small)
> ```
> which means we will continue searching for null-term if length ends at
> the end of a page and there was no null-term in `src`.
>
> The fix is to make the flag:
> ```
> cmpq %r8, %rdx
> jbe L(page_cross_small)
> ```
> ---
> string/test-strncat.c | 25 ++++++++++++++++++++++++-
> sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
> 2 files changed, 26 insertions(+), 3 deletions(-)
>
> diff --git a/string/test-strncat.c b/string/test-strncat.c
> index e03d329e1c..c0cde206ee 100644
> --- a/string/test-strncat.c
> +++ b/string/test-strncat.c
> @@ -28,6 +28,7 @@
> # define CHAR char
> # define UCHAR unsigned char
> # define SIMPLE_STRNCAT simple_strncat
> +# define STRNLEN strnlen
> # define STRLEN strlen
> # define MEMSET memset
> # define MEMCPY memcpy
> @@ -40,6 +41,7 @@
> # define CHAR wchar_t
> # define UCHAR wchar_t
> # define SIMPLE_STRNCAT simple_wcsncat
> +# define STRNLEN wcsnlen
> # define STRLEN wcslen
> # define MEMSET wmemset
> # define MEMCPY wmemcpy
> @@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> return;
> }
>
> - size_t len = STRLEN (src);
> + size_t len = STRNLEN (src, n);
> if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
> {
> error (0, 0, "Incorrect concatenation in function %s",
> @@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> }
> }
>
> +static void
> +do_test_src_no_nullterm_bz30065 (void)
> +{
> + /* NB: "src does not need to be null-terminated if it contains n or more
> + * bytes." */
> + CHAR *s1, *s2;
> + size_t bound = page_size / sizeof (CHAR);
> + s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
> + s2 = (CHAR *) buf2;
> + MEMSET (s1 - bound, -1, bound);
> + for (size_t n = 0; n < bound; ++n)
> + {
> + FOR_EACH_IMPL (impl, 0)
> + {
> + s2[0] = '\0';
> + do_one_test (impl, s2, s1 - n, n);
> + }
> + }
> +}
> +
> static void
> do_test (size_t align1, size_t align2, size_t len1, size_t len2,
> size_t n, int max_char)
> @@ -372,6 +394,7 @@ test_main (void)
>
> do_random_tests ();
> do_overflow_tests ();
> + do_test_src_no_nullterm_bz30065 ();
> return ret;
> }
>
> diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S
> index b380e8e11c..c2ff202238 100644
> --- a/sysdeps/x86_64/multiarch/strncat-avx2.S
> +++ b/sysdeps/x86_64/multiarch/strncat-avx2.S
> @@ -66,7 +66,7 @@ ENTRY(STRNCAT)
> salq $2, %rdx
> # else
> test %rdx, %rdx
> - jl L(zero_len)
> + jle L(zero_len)
> # endif
> vpxor %VZERO_128, %VZERO_128, %VZERO_128
>
> @@ -387,7 +387,7 @@ L(page_cross):
> subl %esi, %r8d
> andl $(VEC_SIZE - 1), %r8d
> cmpq %r8, %rdx
> - jb L(page_cross_small)
> + jbe L(page_cross_small)
>
> /* Optimizing more aggressively for space as this is very cold
> code. This saves 2x cache lines. */
On Tue, Jan 31, 2023 at 7:10 PM Carlos O'Donell via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On 1/31/23 18:46, Noah Goldstein via Libc-alpha wrote:
> > Occurs when `src` has no null-term.
>
> This has been pushed as b2c474f8de4c92bfe7435853a96805ec32d68dfa.
>
> We are now in a hard freeze as I prepare to cut the release.
>
> Please do not commit anything further.
>
> If we find other issues we can backport to the release branch after testing.
>
> I'm re-running testing with this patch included for x86_64 and i686.
>
> > Two cases:
> >
> > 1) Zero-length check is doing:
> > ```
> > test %rdx, %rdx
> > jl L(zero_len)
> > ```
> > which doesn't actually check zero (was at some point `decq` and the
> > flag never got updated).
> >
> > The fix is just make the flag `jle` i.e:
> > ```
> > test %rdx, %rdx
> > jle L(zero_len)
> > ```
> >
> > 2) Length check in page-cross case checking if we should continue is
> > doing:
> > ```
> > cmpq %r8, %rdx
> > jb L(page_cross_small)
> > ```
> > which means we will continue searching for null-term if length ends at
> > the end of a page and there was no null-term in `src`.
> >
> > The fix is to make the flag:
> > ```
> > cmpq %r8, %rdx
> > jbe L(page_cross_small)
> > ```
> > ---
> > string/test-strncat.c | 25 ++++++++++++++++++++++++-
> > sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
> > 2 files changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/string/test-strncat.c b/string/test-strncat.c
> > index e03d329e1c..c0cde206ee 100644
> > --- a/string/test-strncat.c
> > +++ b/string/test-strncat.c
> > @@ -28,6 +28,7 @@
> > # define CHAR char
> > # define UCHAR unsigned char
> > # define SIMPLE_STRNCAT simple_strncat
> > +# define STRNLEN strnlen
> > # define STRLEN strlen
> > # define MEMSET memset
> > # define MEMCPY memcpy
> > @@ -40,6 +41,7 @@
> > # define CHAR wchar_t
> > # define UCHAR wchar_t
> > # define SIMPLE_STRNCAT simple_wcsncat
> > +# define STRNLEN wcsnlen
> > # define STRLEN wcslen
> > # define MEMSET wmemset
> > # define MEMCPY wmemcpy
> > @@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> > return;
> > }
> >
> > - size_t len = STRLEN (src);
> > + size_t len = STRNLEN (src, n);
> > if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
> > {
> > error (0, 0, "Incorrect concatenation in function %s",
> > @@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> > }
> > }
> >
> > +static void
> > +do_test_src_no_nullterm_bz30065 (void)
> > +{
> > + /* NB: "src does not need to be null-terminated if it contains n or more
> > + * bytes." */
> > + CHAR *s1, *s2;
> > + size_t bound = page_size / sizeof (CHAR);
> > + s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
> > + s2 = (CHAR *) buf2;
> > + MEMSET (s1 - bound, -1, bound);
> > + for (size_t n = 0; n < bound; ++n)
> > + {
> > + FOR_EACH_IMPL (impl, 0)
> > + {
> > + s2[0] = '\0';
> > + do_one_test (impl, s2, s1 - n, n);
> > + }
> > + }
> > +}
> > +
> > static void
> > do_test (size_t align1, size_t align2, size_t len1, size_t len2,
> > size_t n, int max_char)
> > @@ -372,6 +394,7 @@ test_main (void)
> >
> > do_random_tests ();
> > do_overflow_tests ();
> > + do_test_src_no_nullterm_bz30065 ();
> > return ret;
> > }
> >
> > diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S
> > index b380e8e11c..c2ff202238 100644
> > --- a/sysdeps/x86_64/multiarch/strncat-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/strncat-avx2.S
> > @@ -66,7 +66,7 @@ ENTRY(STRNCAT)
> > salq $2, %rdx
> > # else
> > test %rdx, %rdx
> > - jl L(zero_len)
> > + jle L(zero_len)
> > # endif
> > vpxor %VZERO_128, %VZERO_128, %VZERO_128
> >
> > @@ -387,7 +387,7 @@ L(page_cross):
> > subl %esi, %r8d
> > andl $(VEC_SIZE - 1), %r8d
> > cmpq %r8, %rdx
> > - jb L(page_cross_small)
> > + jbe L(page_cross_small)
> >
> > /* Optimizing more aggressively for space as this is very cold
> > code. This saves 2x cache lines. */
>
> --
> Cheers,
> Carlos.
>
I would like to backport this patch to release branches.
Any comments or objections?
--Sunil
On Sat, Feb 11, 2023 at 5:00 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
>
> On Tue, Jan 31, 2023 at 7:10 PM Carlos O'Donell via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > On 1/31/23 18:46, Noah Goldstein via Libc-alpha wrote:
> > > Occurs when `src` has no null-term.
> >
> > This has been pushed as b2c474f8de4c92bfe7435853a96805ec32d68dfa.
> >
> > We are now in a hard freeze as I prepare to cut the release.
> >
> > Please do not commit anything further.
> >
> > If we find other issues we can backport to the release branch after testing.
> >
> > I'm re-running testing with this patch included for x86_64 and i686.
> >
> > > Two cases:
> > >
> > > 1) Zero-length check is doing:
> > > ```
> > > test %rdx, %rdx
> > > jl L(zero_len)
> > > ```
> > > which doesn't actually check zero (was at some point `decq` and the
> > > flag never got updated).
> > >
> > > The fix is just make the flag `jle` i.e:
> > > ```
> > > test %rdx, %rdx
> > > jle L(zero_len)
> > > ```
> > >
> > > 2) Length check in page-cross case checking if we should continue is
> > > doing:
> > > ```
> > > cmpq %r8, %rdx
> > > jb L(page_cross_small)
> > > ```
> > > which means we will continue searching for null-term if length ends at
> > > the end of a page and there was no null-term in `src`.
> > >
> > > The fix is to make the flag:
> > > ```
> > > cmpq %r8, %rdx
> > > jbe L(page_cross_small)
> > > ```
> > > ---
> > > string/test-strncat.c | 25 ++++++++++++++++++++++++-
> > > sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
> > > 2 files changed, 26 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/string/test-strncat.c b/string/test-strncat.c
> > > index e03d329e1c..c0cde206ee 100644
> > > --- a/string/test-strncat.c
> > > +++ b/string/test-strncat.c
> > > @@ -28,6 +28,7 @@
> > > # define CHAR char
> > > # define UCHAR unsigned char
> > > # define SIMPLE_STRNCAT simple_strncat
> > > +# define STRNLEN strnlen
> > > # define STRLEN strlen
> > > # define MEMSET memset
> > > # define MEMCPY memcpy
> > > @@ -40,6 +41,7 @@
> > > # define CHAR wchar_t
> > > # define UCHAR wchar_t
> > > # define SIMPLE_STRNCAT simple_wcsncat
> > > +# define STRNLEN wcsnlen
> > > # define STRLEN wcslen
> > > # define MEMSET wmemset
> > > # define MEMCPY wmemcpy
> > > @@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> > > return;
> > > }
> > >
> > > - size_t len = STRLEN (src);
> > > + size_t len = STRNLEN (src, n);
> > > if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
> > > {
> > > error (0, 0, "Incorrect concatenation in function %s",
> > > @@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
> > > }
> > > }
> > >
> > > +static void
> > > +do_test_src_no_nullterm_bz30065 (void)
> > > +{
> > > + /* NB: "src does not need to be null-terminated if it contains n or more
> > > + * bytes." */
> > > + CHAR *s1, *s2;
> > > + size_t bound = page_size / sizeof (CHAR);
> > > + s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
> > > + s2 = (CHAR *) buf2;
> > > + MEMSET (s1 - bound, -1, bound);
> > > + for (size_t n = 0; n < bound; ++n)
> > > + {
> > > + FOR_EACH_IMPL (impl, 0)
> > > + {
> > > + s2[0] = '\0';
> > > + do_one_test (impl, s2, s1 - n, n);
> > > + }
> > > + }
> > > +}
> > > +
> > > static void
> > > do_test (size_t align1, size_t align2, size_t len1, size_t len2,
> > > size_t n, int max_char)
> > > @@ -372,6 +394,7 @@ test_main (void)
> > >
> > > do_random_tests ();
> > > do_overflow_tests ();
> > > + do_test_src_no_nullterm_bz30065 ();
> > > return ret;
> > > }
> > >
> > > diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S
> > > index b380e8e11c..c2ff202238 100644
> > > --- a/sysdeps/x86_64/multiarch/strncat-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/strncat-avx2.S
> > > @@ -66,7 +66,7 @@ ENTRY(STRNCAT)
> > > salq $2, %rdx
> > > # else
> > > test %rdx, %rdx
> > > - jl L(zero_len)
> > > + jle L(zero_len)
> > > # endif
> > > vpxor %VZERO_128, %VZERO_128, %VZERO_128
> > >
> > > @@ -387,7 +387,7 @@ L(page_cross):
> > > subl %esi, %r8d
> > > andl $(VEC_SIZE - 1), %r8d
> > > cmpq %r8, %rdx
> > > - jb L(page_cross_small)
> > > + jbe L(page_cross_small)
> > >
> > > /* Optimizing more aggressively for space as this is very cold
> > > code. This saves 2x cache lines. */
> >
> > --
> > Cheers,
> > Carlos.
> >
>
> I would like to backport this patch to release branches.
> Any comments or objections?
>
> --Sunil
OK.
Thanks.
@@ -28,6 +28,7 @@
# define CHAR char
# define UCHAR unsigned char
# define SIMPLE_STRNCAT simple_strncat
+# define STRNLEN strnlen
# define STRLEN strlen
# define MEMSET memset
# define MEMCPY memcpy
@@ -40,6 +41,7 @@
# define CHAR wchar_t
# define UCHAR wchar_t
# define SIMPLE_STRNCAT simple_wcsncat
+# define STRNLEN wcsnlen
# define STRLEN wcslen
# define MEMSET wmemset
# define MEMCPY wmemcpy
@@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
return;
}
- size_t len = STRLEN (src);
+ size_t len = STRNLEN (src, n);
if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
{
error (0, 0, "Incorrect concatenation in function %s",
@@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
}
}
+static void
+do_test_src_no_nullterm_bz30065 (void)
+{
+ /* NB: "src does not need to be null-terminated if it contains n or more
+ * bytes." */
+ CHAR *s1, *s2;
+ size_t bound = page_size / sizeof (CHAR);
+ s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
+ s2 = (CHAR *) buf2;
+ MEMSET (s1 - bound, -1, bound);
+ for (size_t n = 0; n < bound; ++n)
+ {
+ FOR_EACH_IMPL (impl, 0)
+ {
+ s2[0] = '\0';
+ do_one_test (impl, s2, s1 - n, n);
+ }
+ }
+}
+
static void
do_test (size_t align1, size_t align2, size_t len1, size_t len2,
size_t n, int max_char)
@@ -372,6 +394,7 @@ test_main (void)
do_random_tests ();
do_overflow_tests ();
+ do_test_src_no_nullterm_bz30065 ();
return ret;
}
@@ -66,7 +66,7 @@ ENTRY(STRNCAT)
salq $2, %rdx
# else
test %rdx, %rdx
- jl L(zero_len)
+ jle L(zero_len)
# endif
vpxor %VZERO_128, %VZERO_128, %VZERO_128
@@ -387,7 +387,7 @@ L(page_cross):
subl %esi, %r8d
andl $(VEC_SIZE - 1), %r8d
cmpq %r8, %rdx
- jb L(page_cross_small)
+ jbe L(page_cross_small)
/* Optimizing more aggressively for space as this is very cold
code. This saves 2x cache lines. */