6.18-stable review patch. If anyone has any objections, please let me know.
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From: Fernando Fernandez Mancera fmancera@suse.de
[ Upstream commit 69894e5b4c5e28cda5f32af33d4a92b7a4b93b0e ]
Connlimit expression can be used for all kind of packets and not only for packets with connection state new. See this ruleset as example:
table ip filter { chain input { type filter hook input priority filter; policy accept; tcp dport 22 ct count over 4 counter } }
Currently, if the connection count goes over the limit the counter will count the packets. When a connection is closed, the connection count won't decrement as it should because it is only updated for new connections due to an optimization on __nf_conncount_add() that prevents updating the list if the connection is duplicated.
To solve this problem, check whether the connection was skipped and if so, update the list. Adjust count_tree() too so the same fix is applied for xt_connlimit.
Fixes: 976afca1ceba ("netfilter: nf_conncount: Early exit in nf_conncount_lookup() and cleanup") Closes: https://lore.kernel.org/netfilter/trinity-85c72a88-d762-46c3-be97-36f10e5d97... Signed-off-by: Fernando Fernandez Mancera fmancera@suse.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/nf_conncount.c | 12 ++++++++---- net/netfilter/nft_connlimit.c | 13 +++++++++++-- 2 files changed, 19 insertions(+), 6 deletions(-)
diff --git a/net/netfilter/nf_conncount.c b/net/netfilter/nf_conncount.c index 0ffc5ff78a714..b84cfb5616df4 100644 --- a/net/netfilter/nf_conncount.c +++ b/net/netfilter/nf_conncount.c @@ -179,7 +179,7 @@ static int __nf_conncount_add(struct net *net, if (ct && nf_ct_is_confirmed(ct)) { if (refcounted) nf_ct_put(ct); - return 0; + return -EEXIST; }
if ((u32)jiffies == list->last_gc) @@ -398,7 +398,7 @@ insert_tree(struct net *net, int ret;
ret = nf_conncount_add_skb(net, skb, l3num, &rbconn->list); - if (ret) + if (ret && ret != -EEXIST) count = 0; /* hotdrop */ else count = rbconn->list.count; @@ -501,10 +501,14 @@ count_tree(struct net *net, /* same source network -> be counted! */ ret = __nf_conncount_add(net, skb, l3num, &rbconn->list); spin_unlock_bh(&rbconn->list.list_lock); - if (ret) + if (ret && ret != -EEXIST) { return 0; /* hotdrop */ - else + } else { + /* -EEXIST means add was skipped, update the list */ + if (ret == -EEXIST) + nf_conncount_gc_list(net, &rbconn->list); return rbconn->list.count; + } } }
diff --git a/net/netfilter/nft_connlimit.c b/net/netfilter/nft_connlimit.c index 5df7134131d29..d4964087bbc5e 100644 --- a/net/netfilter/nft_connlimit.c +++ b/net/netfilter/nft_connlimit.c @@ -29,8 +29,17 @@ static inline void nft_connlimit_do_eval(struct nft_connlimit *priv,
err = nf_conncount_add_skb(nft_net(pkt), pkt->skb, nft_pf(pkt), priv->list); if (err) { - regs->verdict.code = NF_DROP; - return; + if (err == -EEXIST) { + /* Call gc to update the list count if any connection has + * been closed already. This is useful for softlimit + * connections like limiting bandwidth based on a number + * of open connections. + */ + nf_conncount_gc_list(nft_net(pkt), priv->list); + } else { + regs->verdict.code = NF_DROP; + return; + } }
count = READ_ONCE(priv->list->count);