nf_conntrack: avoid kernel pointer value leak in slab name

nf_conntrack: avoid kernel pointer value leak in slab name

Orabug: 25227158

[ Upstream commit 31b0b385f69d8d5491a4bca288e25e63f1d945d0 ]

The slab name ends up being visible in the directory structure under
/sys, and even if you don't have access rights to the file you can see
the filenames.

Just use a 64-bit counter instead of the pointer to the 'net' structure
to generate a unique name.

This code will go away in 4.7 when the conntrack code moves to a single
kmemcache, but this is the backportable simple solution to avoiding
leaking kernel pointers to user space.

Fixes: 5b3501faa874 ("netfilter: nf_conntrack: per netns nf_conntrack_cachep")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 8de861b16d946b7c0ce246fcbb65d550c357c65c)

Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>