Re: [GIT PULL] [IPV6] COMPAT: Fix SSM applications on 64bit kernels.

[David Miller <davem@davemloft.net>]

From: David Stevens <dlstevens@us.ibm.com>
Date: Thu, 24 Apr 2008 11:52:01 -0600

> I was looking at this problem too, and below is what I have at the
> moment. I've only tested the group_req portion, and I was looking
> at putting this in net/compat.c with hooks back, since the code is
> literally identical for IPv4 except the sockopt function you call at
> the end, but I've moved it to ipv6_sockglue.c for this patch.
> 
> This touches a lot less code and I think comes out a lot smaller.
> 
> Method is to translate to padded version on the user stack, make
> the call, and translate back (in the MSFILTER case) on return, as
> is done for some other compat functions.

I've looked at both approaches.

David's might be the better way to do this, as an initial
approximation.

I think we can combine ideas from both implementations, so why don't
we do the following:

1) Use copy_in_user() as that's the proper interaface to copy within
   userspace in COMPAT code.

2) Use aligned(4) attribute instead of packed, this will help RISC
   compat systems a lot

If you make these changes and do some testing, I think this is the
patch I will apply.

Thanks.