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author | Liping Zhang <liping.zhang@spreadtrum.com> | 2016-08-18 20:39:05 +0800 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2016-08-18 15:17:00 +0200 |
commit | b75911b66ad508a3c3f006ce37d9f9ebee34da43 (patch) | |
tree | 814e6b6bdeb4b62100669370608b10f4d46497ec /net/netfilter/nfnetlink_cttimeout.c | |
parent | 12be15dd5ac928b60323b1ed8f6facd7335bb2cc (diff) | |
download | op-kernel-dev-b75911b66ad508a3c3f006ce37d9f9ebee34da43.zip op-kernel-dev-b75911b66ad508a3c3f006ce37d9f9ebee34da43.tar.gz |
netfilter: cttimeout: fix use after free error when delete netns
In general, when we want to delete a netns, cttimeout_net_exit will
be called before ipt_unregister_table, i.e. before ctnl_timeout_put.
But after call kfree_rcu in cttimeout_net_exit, we will still decrease
the timeout object's refcnt in ctnl_timeout_put, this is incorrect,
and will cause a use after free error.
It is easy to reproduce this problem:
# while : ; do
ip netns add xxx
ip netns exec xxx nfct add timeout testx inet icmp timeout 200
ip netns exec xxx iptables -t raw -p icmp -I OUTPUT -j CT --timeout testx
ip netns del xxx
done
=======================================================================
BUG kmalloc-96 (Tainted: G B E ): Poison overwritten
-----------------------------------------------------------------------
INFO: 0xffff88002b5161e8-0xffff88002b5161e8. First byte 0x6a instead of
0x6b
INFO: Allocated in cttimeout_new_timeout+0xd4/0x240 [nfnetlink_cttimeout]
age=104 cpu=0 pid=3330
___slab_alloc+0x4da/0x540
__slab_alloc+0x20/0x40
__kmalloc+0x1c8/0x240
cttimeout_new_timeout+0xd4/0x240 [nfnetlink_cttimeout]
nfnetlink_rcv_msg+0x21a/0x230 [nfnetlink]
[ ... ]
So only when the refcnt decreased to 0, we call kfree_rcu to free the
timeout object. And like nfnetlink_acct do, use atomic_cmpxchg to
avoid race between ctnl_timeout_try_del and ctnl_timeout_put.
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net/netfilter/nfnetlink_cttimeout.c')
-rw-r--r-- | net/netfilter/nfnetlink_cttimeout.c | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c index 4cdcd96..68216cd 100644 --- a/net/netfilter/nfnetlink_cttimeout.c +++ b/net/netfilter/nfnetlink_cttimeout.c @@ -330,16 +330,16 @@ static int ctnl_timeout_try_del(struct net *net, struct ctnl_timeout *timeout) { int ret = 0; - /* we want to avoid races with nf_ct_timeout_find_get. */ - if (atomic_dec_and_test(&timeout->refcnt)) { + /* We want to avoid races with ctnl_timeout_put. So only when the + * current refcnt is 1, we decrease it to 0. + */ + if (atomic_cmpxchg(&timeout->refcnt, 1, 0) == 1) { /* We are protected by nfnl mutex. */ list_del_rcu(&timeout->head); nf_ct_l4proto_put(timeout->l4proto); ctnl_untimeout(net, timeout); kfree_rcu(timeout, rcu_head); } else { - /* still in use, restore reference counter. */ - atomic_inc(&timeout->refcnt); ret = -EBUSY; } return ret; @@ -543,7 +543,9 @@ err: static void ctnl_timeout_put(struct ctnl_timeout *timeout) { - atomic_dec(&timeout->refcnt); + if (atomic_dec_and_test(&timeout->refcnt)) + kfree_rcu(timeout, rcu_head); + module_put(THIS_MODULE); } #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ @@ -591,7 +593,9 @@ static void __net_exit cttimeout_net_exit(struct net *net) list_for_each_entry_safe(cur, tmp, &net->nfct_timeout_list, head) { list_del_rcu(&cur->head); nf_ct_l4proto_put(cur->l4proto); - kfree_rcu(cur, rcu_head); + + if (atomic_dec_and_test(&cur->refcnt)) + kfree_rcu(cur, rcu_head); } } |