linux-kernel - [PATCH] amd64: Fix csum_partial_copy

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Date:   Wed, 18 Oct 2023 06:18:05 +0000
From:   gus Gusenleitner Klaus <gus@...a.com>
To:     lkml <linux-kernel@...r.kernel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        gus Gusenleitner Klaus <gus@...a.com>,
        "David S. Miller" <davem@...emloft.net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] amd64: Fix csum_partial_copy_generic()

The checksum calculation is wrong in case of an source buffer
containing zero bytes only. The expected return value is 0, the
actual return value is 0xfffffff.

This problem occurs when a ICMP echo reply is sent that has set
zero identifier, sequence number and data.

Signed-off-by: Klaus Gusenleitner <gus@...a.com>
---
 arch/x86/lib/csum-copy_64.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/lib/csum-copy_64.S b/arch/x86/lib/csum-copy_64.S
index d9e16a2cf285..c8391b4f3dea 100644
--- a/arch/x86/lib/csum-copy_64.S
+++ b/arch/x86/lib/csum-copy_64.S
@@ -44,7 +44,7 @@ SYM_FUNC_START(csum_partial_copy_generic)
        movq  %r13, 3*8(%rsp)
        movq  %r15, 4*8(%rsp)

-       movl  $-1, %eax
+       movl  $0, %eax
        xorl  %r9d, %r9d
        movl  %edx, %ecx
        cmpl  $8, %ecx
--
2.30.2