From 53b56da83d7899de375a9de153fd7f5397de85e6 Mon Sep 17 00:00:00 2001 From: Liping Zhang Date: Mon, 17 Apr 2017 21:18:57 +0800 Subject: netfilter: ctnetlink: make it safer when updating ct->status After converting to use rcu for conntrack hash, one CPU may update the ct->status via ctnetlink, while another CPU may process the packets and update the ct->status. So the non-atomic operation "ct->status |= status;" via ctnetlink becomes unsafe, and this may clear the IPS_DYING_BIT bit set by another CPU unexpectedly. For example: CPU0 CPU1 ctnetlink_change_status __nf_conntrack_find_get old = ct->status nf_ct_gc_expired - nf_ct_kill - test_and_set_bit(IPS_DYING_BIT new = old | status; - ct->status = new; <-- oops, _DYING_ is cleared! Now using a series of atomic bit operation to solve the above issue. Also note, user shouldn't set IPS_TEMPLATE, IPS_SEQ_ADJUST directly, so make these two bits be unchangable too. If we set the IPS_TEMPLATE_BIT, ct will be freed by nf_ct_tmpl_free, but actually it is alloced by nf_conntrack_alloc. If we set the IPS_SEQ_ADJUST_BIT, this may cause the NULL pointer deference, as the nfct_seqadj(ct) maybe NULL. Last, add some comments to describe the logic change due to the commit a963d710f367 ("netfilter: ctnetlink: Fix regression in CTA_STATUS processing"), which makes me feel a little confusing. Fixes: 76507f69c44e ("[NETFILTER]: nf_conntrack: use RCU for conntrack hash") Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- include/uapi/linux/netfilter/nf_conntrack_common.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/netfilter/nf_conntrack_common.h b/include/uapi/linux/netfilter/nf_conntrack_common.h index 6a8e33dd4ecb..38fc383139f0 100644 --- a/include/uapi/linux/netfilter/nf_conntrack_common.h +++ b/include/uapi/linux/netfilter/nf_conntrack_common.h @@ -82,10 +82,6 @@ enum ip_conntrack_status { IPS_DYING_BIT = 9, IPS_DYING = (1 << IPS_DYING_BIT), - /* Bits that cannot be altered from userland. */ - IPS_UNCHANGEABLE_MASK = (IPS_NAT_DONE_MASK | IPS_NAT_MASK | - IPS_EXPECTED | IPS_CONFIRMED | IPS_DYING), - /* Connection has fixed timeout. */ IPS_FIXED_TIMEOUT_BIT = 10, IPS_FIXED_TIMEOUT = (1 << IPS_FIXED_TIMEOUT_BIT), @@ -101,6 +97,15 @@ enum ip_conntrack_status { /* Conntrack got a helper explicitly attached via CT target. */ IPS_HELPER_BIT = 13, IPS_HELPER = (1 << IPS_HELPER_BIT), + + /* Be careful here, modifying these bits can make things messy, + * so don't let users modify them directly. + */ + IPS_UNCHANGEABLE_MASK = (IPS_NAT_DONE_MASK | IPS_NAT_MASK | + IPS_EXPECTED | IPS_CONFIRMED | IPS_DYING | + IPS_SEQ_ADJUST | IPS_TEMPLATE), + + __IPS_MAX_BIT = 14, }; /* Connection tracking event types */ -- cgit