[v3,2/7] x86: Fix __wcsncmp_evex in strcmp-evex.S [BZ# 28755]
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Commit Message
Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to
__wcscmp_evex. For x86_64 this covers the entire address range so any
length larger could not possibly be used to bound `s1` or `s2`.
test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass.
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
sysdeps/x86_64/multiarch/strcmp-evex.S | 10 ++++++++++
1 file changed, 10 insertions(+)
Comments
On Mon, Jan 10, 2022 at 1:36 PM Noah Goldstein via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to
> __wcscmp_evex. For x86_64 this covers the entire address range so any
> length larger could not possibly be used to bound `s1` or `s2`.
>
> test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass.
>
> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
> sysdeps/x86_64/multiarch/strcmp-evex.S | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> index 1d971f3889..0cd939d5af 100644
> --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> @@ -104,6 +104,16 @@ ENTRY (STRCMP)
> je L(char0)
> jb L(zero)
> # ifdef USE_AS_WCSCMP
> +# ifndef __ILP32__
> + movq %rdx, %rcx
> + /* Check if length could overflow when multiplied by
> + sizeof(wchar_t). Checking top 8 bits will cover all potential
> + overflow cases as well as redirect cases where its impossible to
> + length to bound a valid memory region. In these cases just use
> + 'wcscmp'. */
> + shrq $56, %rcx
> + jnz __wcscmp_evex
> +# endif
> /* Convert units: from wide to byte char. */
> shl $2, %RDX_LP
> # endif
> --
> 2.25.1
>
LGTM.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Thanks.
On Mon, Jan 10, 2022 at 6:15 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Mon, Jan 10, 2022 at 1:36 PM Noah Goldstein via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to
> > __wcscmp_evex. For x86_64 this covers the entire address range so any
> > length larger could not possibly be used to bound `s1` or `s2`.
> >
> > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> > sysdeps/x86_64/multiarch/strcmp-evex.S | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > index 1d971f3889..0cd939d5af 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > @@ -104,6 +104,16 @@ ENTRY (STRCMP)
> > je L(char0)
> > jb L(zero)
> > # ifdef USE_AS_WCSCMP
> > +# ifndef __ILP32__
> > + movq %rdx, %rcx
> > + /* Check if length could overflow when multiplied by
> > + sizeof(wchar_t). Checking top 8 bits will cover all potential
> > + overflow cases as well as redirect cases where its impossible to
> > + length to bound a valid memory region. In these cases just use
> > + 'wcscmp'. */
> > + shrq $56, %rcx
> > + jnz __wcscmp_evex
> > +# endif
> > /* Convert units: from wide to byte char. */
> > shl $2, %RDX_LP
> > # endif
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.
I am backporting this to 2.34 branch.
On Wed, Jan 26, 2022 at 2:06 PM H.J. Lu via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Mon, Jan 10, 2022 at 6:15 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Mon, Jan 10, 2022 at 1:36 PM Noah Goldstein via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> > >
> > > Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to
> > > __wcscmp_evex. For x86_64 this covers the entire address range so any
> > > length larger could not possibly be used to bound `s1` or `s2`.
> > >
> > > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass.
> > >
> > > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > > ---
> > > sysdeps/x86_64/multiarch/strcmp-evex.S | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > index 1d971f3889..0cd939d5af 100644
> > > --- a/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
> > > @@ -104,6 +104,16 @@ ENTRY (STRCMP)
> > > je L(char0)
> > > jb L(zero)
> > > # ifdef USE_AS_WCSCMP
> > > +# ifndef __ILP32__
> > > + movq %rdx, %rcx
> > > + /* Check if length could overflow when multiplied by
> > > + sizeof(wchar_t). Checking top 8 bits will cover all potential
> > > + overflow cases as well as redirect cases where its impossible to
> > > + length to bound a valid memory region. In these cases just use
> > > + 'wcscmp'. */
> > > + shrq $56, %rcx
> > > + jnz __wcscmp_evex
> > > +# endif
> > > /* Convert units: from wide to byte char. */
> > > shl $2, %RDX_LP
> > > # endif
> > > --
> > > 2.25.1
> > >
> >
> > LGTM.
> >
> > Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
> >
> > Thanks.
> >
> > --
> > H.J.
>
> I am backporting this to 2.34 branch.
>
> --
> H.J.
I would like to backport this patch to release branches.
Any comments or objections?
--Sunil
@@ -104,6 +104,16 @@ ENTRY (STRCMP)
je L(char0)
jb L(zero)
# ifdef USE_AS_WCSCMP
+# ifndef __ILP32__
+ movq %rdx, %rcx
+ /* Check if length could overflow when multiplied by
+ sizeof(wchar_t). Checking top 8 bits will cover all potential
+ overflow cases as well as redirect cases where its impossible to
+ length to bound a valid memory region. In these cases just use
+ 'wcscmp'. */
+ shrq $56, %rcx
+ jnz __wcscmp_evex
+# endif
/* Convert units: from wide to byte char. */
shl $2, %RDX_LP
# endif