From 26b2bd70d22457556e2fa01cbf1192cb1a94d619 Mon Sep 17 00:00:00 2001 From: Ilya Maximets Date: Mon, 21 Sep 2026 16:55:43 +0200 Subject: net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry In a case where skb with an unconfirmed ct entry gets cloned, we may end up committing both but with different sets of extensions. The series of events: 1. The first clone wants to commit and runs the helpers wiring up the extension pointer into the expectation list. 2. Then it looses the confirmation keeping the entry unconfirmed. 3. Second clone now wants to commit labels and adds the new extension for that breaking the pointer in the expectation list causing UAF on the destruction path later. While this is possible to trigger, there should be no practical network pipeline where committing both clones without modifications into the same zone is needed. So, let's just reset the entry in case for some reason we got an skb with a shared one during commit. This doesn't affect any known use cases, but avoids any potential problems with sharing and modification of the unconfirmed ct entry. The fixes tag points to the introduction of helpers, since that's the main UAF trigger for the sharing. Fixes: cae3a2627520 ("openvswitch: Allow attaching helpers to ct action") Cc: stable@vger.kernel.org Reported-by: Axel Mierczuk Signed-off-by: Ilya Maximets Reviewed-by: Aaron Conole Link: https://patch.msgid.link/20260921145655.3167436-2-i.maximets@ovn.org Signed-off-by: Jakub Kicinski --- include/net/netfilter/nf_conntrack.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include') diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h index bc42dd0e10e6..c39425e54d87 100644 --- a/include/net/netfilter/nf_conntrack.h +++ b/include/net/netfilter/nf_conntrack.h @@ -185,6 +185,11 @@ static inline void nf_ct_put(struct nf_conn *ct) nf_ct_destroy(&ct->ct_general); } +static inline bool nf_ct_shared(const struct nf_conn *ct) +{ + return refcount_read(&ct->ct_general.use) > 1; +} + /* load module; enable/disable conntrack in this namespace */ int nf_ct_netns_get(struct net *net, u8 nfproto); void nf_ct_netns_put(struct net *net, u8 nfproto); -- cgit v1.2.3