MIPS: Fix special case in 64 bit IP checksumming.

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>
Cc: stable@vger.kernel.org
Signed-off-by: James Hogan <james.hogan@imgtec.com>

diff --git a/arch/mips/include/asm/checksum.h b/arch/mips/include/asm/checksum.h
index 7749daf2a46594cbf9c2dc9a6334fbcd514ca3a5..c8b574f7e0ccc293c4e1ae7d1a862328ac906648 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, __be32 daddr,
        "       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)