[PATCH 1/2] MPILIB: Fix comparison of negative MPIs

[PATCH 1/2] MPILIB: Fix comparison of negative MPIs

[Rasmus Villemoes]

If u and v both represent negative integers and their limb counts
happen to differ, mpi_cmp will always return a positive value - this
is obviously bogus. u is smaller than v if and only if it is larger in
absolute value.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 lib/mpi/mpi-cmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
index 1871e7b61ca0..3801694240d8 100644
--- a/lib/mpi/mpi-cmp.c
+++ b/lib/mpi/mpi-cmp.c
@@ -57,7 +57,7 @@ int mpi_cmp(MPI u, MPI v)
 	if (usize != vsize && !u->sign && !v->sign)
 		return usize - vsize;
 	if (usize != vsize && u->sign && v->sign)
-		return vsize + usize;
+		return vsize - usize;
 	if (!usize)
 		return 0;
 	cmp = mpihelp_cmp(u->d, v->d, usize);
-- 
2.1.3

[PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

[Rasmus Villemoes]

The condition preceding 'return 1;' makes my head hurt. At this point,
we know that u and v have the same sign; if they are negative, they
compare opposite to how their absolute values compare (which
mpihelp_cmp found for us), otherwise cmp itself is the
answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
-INT_MIN==INT_MIN won't bite us.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 lib/mpi/mpi-cmp.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
index 3801694240d8..d25e9e96c310 100644
--- a/lib/mpi/mpi-cmp.c
+++ b/lib/mpi/mpi-cmp.c
@@ -61,10 +61,8 @@ int mpi_cmp(MPI u, MPI v)
 	if (!usize)
 		return 0;
 	cmp = mpihelp_cmp(u->d, v->d, usize);
-	if (!cmp)
-		return 0;
-	if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
-		return 1;
-	return -1;
+	if (u->sign)
+		return -cmp;
+	return cmp;
 }
 EXPORT_SYMBOL_GPL(mpi_cmp);
-- 
2.1.3

Re: [PATCH 1/2] MPILIB: Fix comparison of negative MPIs

[David Howells]

I think you're right - *adding* the two sizes makes no sense.  cc'ing Dmitry
also for his check.

David


Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> If u and v both represent negative integers and their limb counts
> happen to differ, mpi_cmp will always return a positive value - this
> is obviously bogus. u is smaller than v if and only if it is larger in
> absolute value.
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
>  lib/mpi/mpi-cmp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
> index 1871e7b61ca0..3801694240d8 100644
> --- a/lib/mpi/mpi-cmp.c
> +++ b/lib/mpi/mpi-cmp.c
> @@ -57,7 +57,7 @@ int mpi_cmp(MPI u, MPI v)
>  	if (usize != vsize && !u->sign && !v->sign)
>  		return usize - vsize;
>  	if (usize != vsize && u->sign && v->sign)
> -		return vsize + usize;
> +		return vsize - usize;
>  	if (!usize)
>  		return 0;
>  	cmp = mpihelp_cmp(u->d, v->d, usize);
> -- 
> 2.1.3
> 

Re: [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

[David Howells]

This looks very reasonable.  cc'ing Dmitry for his check.

David
---
Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> The condition preceding 'return 1;' makes my head hurt. At this point,
> we know that u and v have the same sign; if they are negative, they
> compare opposite to how their absolute values compare (which
> mpihelp_cmp found for us), otherwise cmp itself is the
> answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
> -INT_MIN==INT_MIN won't bite us.
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
>  lib/mpi/mpi-cmp.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
> index 3801694240d8..d25e9e96c310 100644
> --- a/lib/mpi/mpi-cmp.c
> +++ b/lib/mpi/mpi-cmp.c
> @@ -61,10 +61,8 @@ int mpi_cmp(MPI u, MPI v)
>  	if (!usize)
>  		return 0;
>  	cmp = mpihelp_cmp(u->d, v->d, usize);
> -	if (!cmp)
> -		return 0;
> -	if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
> -		return 1;
> -	return -1;
> +	if (u->sign)
> +		return -cmp;
> +	return cmp;
>  }
>  EXPORT_SYMBOL_GPL(mpi_cmp);
> -- 
> 2.1.3

Re: [Keyrings] [PATCH 1/2] MPILIB: Fix comparison of negative MPIs

[Dmitry Kasatkin]

Hi,

Thank you. It looks correct.

Ack.

- Dmitry

On 9 January 2015 at 12:58, David Howells <dhowells@redhat.com> wrote:
> I think you're right - *adding* the two sizes makes no sense.  cc'ing Dmitry
> also for his check.
>
> David
>
>
> Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
>
>> If u and v both represent negative integers and their limb counts
>> happen to differ, mpi_cmp will always return a positive value - this
>> is obviously bogus. u is smaller than v if and only if it is larger in
>> absolute value.
>>
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>> ---
>>  lib/mpi/mpi-cmp.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
>> index 1871e7b61ca0..3801694240d8 100644
>> --- a/lib/mpi/mpi-cmp.c
>> +++ b/lib/mpi/mpi-cmp.c
>> @@ -57,7 +57,7 @@ int mpi_cmp(MPI u, MPI v)
>>       if (usize != vsize && !u->sign && !v->sign)
>>               return usize - vsize;
>>       if (usize != vsize && u->sign && v->sign)
>> -             return vsize + usize;
>> +             return vsize - usize;
>>       if (!usize)
>>               return 0;
>>       cmp = mpihelp_cmp(u->d, v->d, usize);
>> --
>> 2.1.3
>>
> _______________________________________________
> Keyrings mailing list
> Keyrings@linux-nfs.org
> To change your subscription to this list, please see http://linux-nfs.org/cgi-bin/mailman/listinfo/keyrings



-- 
Thanks,
Dmitry

Re: [Keyrings] [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

[Dmitry Kasatkin]

Hi,

Thank you. Indeed '-cmp' is much more clear.

Ack.

- Dmitry

On 9 January 2015 at 13:00, David Howells <dhowells@redhat.com> wrote:
> This looks very reasonable.  cc'ing Dmitry for his check.
>
> David
> ---
> Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
>
>> The condition preceding 'return 1;' makes my head hurt. At this point,
>> we know that u and v have the same sign; if they are negative, they
>> compare opposite to how their absolute values compare (which
>> mpihelp_cmp found for us), otherwise cmp itself is the
>> answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
>> -INT_MIN==INT_MIN won't bite us.
>>
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>> ---
>>  lib/mpi/mpi-cmp.c | 8 +++-----
>>  1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
>> index 3801694240d8..d25e9e96c310 100644
>> --- a/lib/mpi/mpi-cmp.c
>> +++ b/lib/mpi/mpi-cmp.c
>> @@ -61,10 +61,8 @@ int mpi_cmp(MPI u, MPI v)
>>       if (!usize)
>>               return 0;
>>       cmp = mpihelp_cmp(u->d, v->d, usize);
>> -     if (!cmp)
>> -             return 0;
>> -     if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
>> -             return 1;
>> -     return -1;
>> +     if (u->sign)
>> +             return -cmp;
>> +     return cmp;
>>  }
>>  EXPORT_SYMBOL_GPL(mpi_cmp);
>> --
>> 2.1.3
> _______________________________________________
> Keyrings mailing list
> Keyrings@linux-nfs.org
> To change your subscription to this list, please see http://linux-nfs.org/cgi-bin/mailman/listinfo/keyrings



-- 
Thanks,
Dmitry

Re: [Keyrings] [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

[David Howells]

Dmitry Kasatkin <dmitry.kasatkin@gmail.com> wrote:

> Ack.

To what email address do I translate that now?

	Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>

perchance?

David

Re: [Keyrings] [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

[Dmitry Kasatkin]

correct.

Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>

Dmitry

On 12 January 2015 at 13:43, David Howells <dhowells@redhat.com> wrote:
> Dmitry Kasatkin <dmitry.kasatkin@gmail.com> wrote:
>
>> Ack.
>
> To what email address do I translate that now?
>
>         Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
>
> perchance?
>
> David



-- 
Thanks,
Dmitry