linux-kernel - [PATCH] powerpc/32: fix csum_partial_copy

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Message-Id: <20160801125605.410371A23A2@localhost.localdomain>
Date:	Mon,  1 Aug 2016 14:56:05 +0200 (CEST)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Scott Wood <oss@...error.net>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	stable@...r.kernel.org, antoine.blangy@....fr
Subject: [PATCH] powerpc/32: fix csum_partial_copy_generic()

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

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

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/lib/checksum_32.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
index d90870a..ad0870a 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S
@@ -127,7 +127,8 @@ _GLOBAL(csum_partial_copy_generic)
 	stw	r7,12(r1)
 	stw	r8,8(r1)
 
-	andi.	r0,r4,1			/* is destination address even ? */
+	rlwinm	r0,r4,3,0x8		/* is destination address even ? */
+	rlwnm	r6,r6,r0,0,31		/* swap bytes for odd destination */
 	cmplwi	cr7,r0,0
 	addic	r12,r6,0
 	addi	r6,r4,-4
-- 
2.1.0