net: fix incorrect credentials passing

net: fix incorrect credentials passing

commit 83f1b4ba917db5dc5a061a44b3403ddb6e783494 upstream.

Commit 257b5358b32f ("scm: Capture the full credentials of the scm
sender") changed the credentials passing code to pass in the effective
uid/gid instead of the real uid/gid.

Obviously this doesn't matter most of the time (since normally they are
the same), but it results in differences for suid binaries when the wrong
uid/gid ends up being used.

This just undoes that (presumably unintentional) part of the commit.

Reported-by: Andy Lutomirski <luto@amacapital.net>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: scm_set_cred() does user namespace conversion
 of euid/egid using cred_to_ucred().  Add and use cred_real_to_ucred() to
 do the same thing for real uid/gid.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>