netfilter: conntrack: re-fetch conntrack after insertion
commit 56b14ece upstream. In case the conntrack is clashing, insertion can free skb->_nfct and set skb->_nfct to the already-confirmed entry. This wasn't found before because the conntrack entry and the extension space used to free'd after an rcu grace period, plus the race needs events enabled to trigger. Reported-by: <syzbot+793a590957d9c1b96620@syzkaller.appspotmail.com> Fixes: 71d8c47f ("netfilter: conntrack: introduce clash resolution on insertion race") Fixes: 2ad9d774 ("netfilter: conntrack: free extension area immediately") Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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