[added to the 4.1 stable tree] nf_conntrack: avoid kernel pointer value leak in slab name

[Sasha Levin <sasha.levin@oracle.com>]

From: Linus Torvalds <torvalds@linux-foundation.org>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ 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>
---
 net/netfilter/nf_conntrack_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 13fad86..bc3f791 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1735,6 +1735,7 @@ void nf_conntrack_init_end(void)
 
 int nf_conntrack_init_net(struct net *net)
 {
+	static atomic64_t unique_id;
 	int ret = -ENOMEM;
 	int cpu;
 
@@ -1758,7 +1759,8 @@ int nf_conntrack_init_net(struct net *net)
 	if (!net->ct.stat)
 		goto err_pcpu_lists;
 
-	net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%p", net);
+	net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%llu",
+				(u64)atomic64_inc_return(&unique_id));
 	if (!net->ct.slabname)
 		goto err_slabname;
 
-- 
2.5.0