powerpc: fix csum_ipv6_magic() on little endian platforms

On little endian platforms, csum_ipv6_magic() keeps len and proto in
CPU byte order. This generates a bad results leading to ICMPv6 packets
from other hosts being dropped by powerpc64le platforms.

In order to fix this, len and proto should be converted to network
byte order ie bigendian byte order. However checksumming 0x12345678
and 0x56341278 provide the exact same result so it is enough to
rotate the sum of len and proto by 1 byte.

PPC32 only support bigendian so the fix is needed for PPC64 only

Fixes: e9c4943a107b ("powerpc: Implement csum_ipv6_magic in assembly")
Reported-by: Jianlin Shi <jishi@redhat.com>
Reported-by: Xin Long <lucien.xin@gmail.com>
Cc: <stable@vger.kernel.org> # 4.18+
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/lib/checksum_64.S b/arch/powerpc/lib/checksum_64.S
index 886ed94..d05c8af 100644 (file)
--- a/arch/powerpc/lib/checksum_64.S
+++ b/arch/powerpc/lib/checksum_64.S
@@ -443,6 +443,9 @@ _GLOBAL(csum_ipv6_magic)
        addc    r0, r8, r9
        ld      r10, 0(r4)
        ld      r11, 8(r4)
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+       rotldi  r5, r5, 8
+#endif
        adde    r0, r0, r10
        add     r5, r5, r7
        adde    r0, r0, r11