MIPS: Fix special case in 64 bit IP checksumming.

Author: Ralf Baechle <[email protected]> Thu Jan 26 02:16:47 2017 +0100
Commit: 804bc005ae3e1dda492efd39e4941c43b3365201
Gitweb: https://git.linux-mips.org/g/ralf/linux/804bc005ae3e
Branch: linux-3.11-stable

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'c complement sum, thus an incorrect result will
be generated.

Signed-off-by: Ralf Baechle <[email protected]>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Mark Zhang <[email protected]>
(cherry picked from commit 2d62bbfca63106efe9be36413158cf2169f9e766)

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 arch/mips/include/asm/checksum.h |    2 ++
 1 file changed, 2 insertions(+)