From: Liping Zhang Date: Mon, 17 Apr 2017 13:18:56 +0000 (+0800) Subject: netfilter: ctnetlink: fix deadlock due to acquire _expect_lock twice X-Git-Tag: v4.14-rc1~994^2~11^2~10 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=88be4c09d9008f9ff337cbf48c5d0f06c8f872e7;p=platform%2Fkernel%2Flinux-rpi.git netfilter: ctnetlink: fix deadlock due to acquire _expect_lock twice Currently, ctnetlink_change_conntrack is always protected by _expect_lock, but this will cause a deadlock when deleting the helper from a conntrack, as the _expect_lock will be acquired again by nf_ct_remove_expectations: CPU0 ---- lock(nf_conntrack_expect_lock); lock(nf_conntrack_expect_lock); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by lt-conntrack_gr/12853: #0: (&table[i].mutex){+.+.+.}, at: [] nfnetlink_rcv_msg+0x399/0x6a9 [nfnetlink] #1: (nf_conntrack_expect_lock){+.....}, at: [] ctnetlink_new_conntrack+0x17f/0x408 [nf_conntrack_netlink] Call Trace: dump_stack+0x85/0xc2 __lock_acquire+0x1608/0x1680 ? ctnetlink_parse_tuple_proto+0x10f/0x1c0 [nf_conntrack_netlink] lock_acquire+0x100/0x1f0 ? nf_ct_remove_expectations+0x32/0x90 [nf_conntrack] _raw_spin_lock_bh+0x3f/0x50 ? nf_ct_remove_expectations+0x32/0x90 [nf_conntrack] nf_ct_remove_expectations+0x32/0x90 [nf_conntrack] ctnetlink_change_helper+0xc6/0x190 [nf_conntrack_netlink] ctnetlink_new_conntrack+0x1b2/0x408 [nf_conntrack_netlink] nfnetlink_rcv_msg+0x60a/0x6a9 [nfnetlink] ? nfnetlink_rcv_msg+0x1b9/0x6a9 [nfnetlink] ? nfnetlink_bind+0x1a0/0x1a0 [nfnetlink] netlink_rcv_skb+0xa4/0xc0 nfnetlink_rcv+0x87/0x770 [nfnetlink] Since the operations are unrelated to nf_ct_expect, so we can drop the _expect_lock. Also note, after removing the _expect_lock protection, another CPU may invoke nf_conntrack_helper_unregister, so we should use rcu_read_lock to protect __nf_conntrack_helper_find invoked by ctnetlink_change_helper. Fixes: ca7433df3a67 ("netfilter: conntrack: seperate expect locking from nf_conntrack_lock") Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 48c1845..e5f9777 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -1510,23 +1510,29 @@ static int ctnetlink_change_helper(struct nf_conn *ct, return 0; } + rcu_read_lock(); helper = __nf_conntrack_helper_find(helpname, nf_ct_l3num(ct), nf_ct_protonum(ct)); - if (helper == NULL) + if (helper == NULL) { + rcu_read_unlock(); return -EOPNOTSUPP; + } if (help) { if (help->helper == helper) { /* update private helper data if allowed. */ if (helper->from_nlattr) helper->from_nlattr(helpinfo, ct); - return 0; + err = 0; } else - return -EBUSY; + err = -EBUSY; + } else { + /* we cannot set a helper for an existing conntrack */ + err = -EOPNOTSUPP; } - /* we cannot set a helper for an existing conntrack */ - return -EOPNOTSUPP; + rcu_read_unlock(); + return err; } static int ctnetlink_change_timeout(struct nf_conn *ct, @@ -1945,9 +1951,7 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl, err = -EEXIST; ct = nf_ct_tuplehash_to_ctrack(h); if (!(nlh->nlmsg_flags & NLM_F_EXCL)) { - spin_lock_bh(&nf_conntrack_expect_lock); err = ctnetlink_change_conntrack(ct, cda); - spin_unlock_bh(&nf_conntrack_expect_lock); if (err == 0) { nf_conntrack_eventmask_report((1 << IPCT_REPLY) | (1 << IPCT_ASSURED) | @@ -2342,11 +2346,7 @@ ctnetlink_glue_parse(const struct nlattr *attr, struct nf_conn *ct) if (ret < 0) return ret; - spin_lock_bh(&nf_conntrack_expect_lock); - ret = ctnetlink_glue_parse_ct((const struct nlattr **)cda, ct); - spin_unlock_bh(&nf_conntrack_expect_lock); - - return ret; + return ctnetlink_glue_parse_ct((const struct nlattr **)cda, ct); } static int ctnetlink_glue_exp_parse(const struct nlattr * const *cda,