nf_conntrack: avoid kernel pointer value leak in slab name

commit 31b0b385f69d8d5491a4bca288e25e63f1d945d0 upstream.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 1f4f954c4b47c7ecf763290659e900277ad5cb89..054638c824ddec5013beb066589a56d93ef0c4c0 100644 (file)
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1791,6 +1791,7 @@ void nf_conntrack_init_end(void)
 
 int nf_conntrack_init_net(struct net *net)
 {
+       static atomic64_t unique_id;
        int ret = -ENOMEM;
        int cpu;
 
@@ -1814,7 +1815,8 @@ 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;