MIPS: Fix special case in 64 bit IP checksumming.

commit 66fd848cadaa6be974a8c780fbeb328f0af4d3bd upstream.

For certain arguments such as saddr = 0xc0a8fd60, daddr = 0xc0a8fda1,
len = 80, proto = 17, sum = 0x7eae049d there will be a carry when
folding the intermediate 64 bit checksum to 32 bit but the code doesn't
add the carry back to the one's complement sum, thus an incorrect result
will be generated.

Reported-by: Mark Zhang <bomb.zhang@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index 3ceacde5eb6e4fd3a7b05906ce3fe153b57c8e5c..17f89f9670b2f6d8900e664ea566076ba5d7f2f8 100644 (file)
--- a/arch/mips/include/asm/checksum.h
+++ b/arch/mips/include/asm/checksum.h
@@ -186,7 +186,9 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr,
        "       daddu   %0, %4          \n"
        "       dsll32  $1, %0, 0       \n"
        "       daddu   %0, $1          \n"
+       "       sltu    $1, %0, $1      \n"
        "       dsra32  %0, %0, 0       \n"
+       "       addu    %0, $1          \n"
 #endif
        "       .set    pop"
        : "=r" (sum)