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netfilter: conntrack: re-fetch conntrack after insertion

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commit 56b14ecec9 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: 71d8c47fc6 ("netfilter: conntrack: introduce clash resolution on insertion race")
Fixes: 2ad9d7747c ("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>
This commit is contained in:
Florian Westphal
2022-05-20 00:02:04 +02:00
committed by Greg Kroah-Hartman
parent 9c413a8c8b
commit 01989d7eeb
1 changed files with 6 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
include/net/netfilter/nf_conntrack_core.h
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@@ -58,8 +58,13 @@ static inline int nf_conntrack_confirm(struct sk_buff *skb)
int ret = NF_ACCEPT;
if (ct) {
if (!nf_ct_is_confirmed(ct))
if (!nf_ct_is_confirmed(ct)) {
ret = __nf_conntrack_confirm(skb);
if (ret == NF_ACCEPT)
ct = (struct nf_conn *)skb_nfct(skb);
}
if (likely(ret == NF_ACCEPT))
nf_ct_deliver_cached_events(ct);
}