On Tue, 2016-08-02 at 10:07 +0200, Christophe Leroy wrote:
> 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@xxxxxxxxxxxxxxx
>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
> 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?
-Scott
>
> diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
> index d90870a..0a57fe6 100644
> --- a/arch/powerpc/lib/checksum_32.S
> +++ b/arch/powerpc/lib/checksum_32.S
> @@ -127,8 +127,9 @@ _GLOBAL(csum_partial_copy_generic)
> stw r7,12(r1)
> stw r8,8(r1)
>
> - andi. r0,r4,1 /* is destination
> address even ? */
> - cmplwi cr7,r0,0
> + rlwinm r0,r4,3,0x8
> + rlwnm r6,r6,r0,0,31 /* odd destination address:
> rotate one byte */
> + cmplwi cr7,r0,0 /* is destination address even ? */
> addic r12,r6,0
> addi r6,r4,-4
> neg r0,r4
> @@ -237,7 +238,7 @@ _GLOBAL(csum_partial_copy_generic)
> 66: addze r3,r12
> addi r1,r1,16
> beqlr+ cr7
> - rlwinm r3,r3,8,0,31 /* swap bytes for odd destination
> */
> + rlwinm r3,r3,8,0,31 /* odd destination address:
> rotate one byte */
> blr
>
> /* read fault */
--
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