Re: [PATCH v2] powerpc/32: fix csum_partial_copy_generic()

Le 05/08/2016 à 08:57, Michael Ellerman a écrit :

Alessio Igor Bogani [off-list ref] writes:

quoted

On 4 August 2016 at 05:53, Scott Wood [off-list ref] wrote:

quoted

On Tue, 2016-08-02 at 10:07 +0200, Christophe Leroy wrote:

quoted

commit 7aef4136566b0 ("powerpc32: rewrite csum_partial_copy_generic()
based on copy_tofrom_user()") introduced a bug when destination
address is odd and initial csum is not null

In that (rare) case the initial csum value has to be rotated one byte
as well as the resulting value is

This patch also fixes related comments

Fixes: 7aef4136566b0 ("powerpc32: rewrite csum_partial_copy_generic()
based on copy_tofrom_user()")
Cc: stable@vger.kernel.org

Signed-off-by: Christophe Leroy <redacted>
---
  v2: updated comments as suggested by Segher

  arch/powerpc/lib/checksum_32.S | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

Alessio, can you confirm whether this fixes the problem you reported?

No unfortunately.

Thanks for testing.

I've dropped the patch for now, send me a new one that works.

The purpose of this patch was not to address Alessio's issue, but to fix 
a huge issue on checksum calculation which induces breakdown of TCP 
connections.

I think it is worth commiting it upstream and on impacted stable 
releases, allthought we don't have yet identified the issue Alessio's has.

Christophe