[PATCH 4.5 101/101] nf_conntrack: avoid kernel pointer value leak in slab name

Greg Kroah-Hartman
2016-05-17T01:29:00Z

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

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1780,6 +1780,7 @@ void nf_conntrack_init_end(void)

int nf_conntrack_init_net(struct net *net)
{
+ static atomic64_t unique_id;
int ret = -ENOMEM;
int cpu;

@@ -1802,7 +1803,8 @@ int nf_conntrack_init_net(struct net *ne
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;