Commits
Liping Zhang committed 88be4c09d90
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: [<ffffffffa05e2009>]
nfnetlink_rcv_msg+0x399/0x6a9 [nfnetlink]
#1: (nf_conntrack_expect_lock){+.....}, at: [<ffffffffa05f2c1f>]
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 <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>