From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Hyunwoo Kim <imv4bel@gmail.com>
Cc: fw@strlen.de, phil@nwl.cc, davem@davemloft.net,
edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
horms@kernel.org, netfilter-devel@vger.kernel.org,
coreteam@netfilter.org, netdev@vger.kernel.org
Subject: Re: [PATCH net] netfilter: nf_flow_table_offload: fix heap overflow in flow_action_entry_next()
Date: Thu, 26 Mar 2026 22:32:50 +0100 [thread overview]
Message-ID: <acWmAgx8xn01nUTD@chamomile> (raw)
In-Reply-To: <aaxe-uH2Qr6qM4E9@v4bel>
On Sun, Mar 08, 2026 at 02:23:06AM +0900, Hyunwoo Kim wrote:
> flow_action_entry_next() increments num_entries and returns a pointer
> into the flow_action_entry array without any bounds checking. The array
> is allocated with a fixed size of NF_FLOW_RULE_ACTION_MAX (16) entries,
> but certain combinations of IPv6 + SNAT + DNAT + double VLAN (QinQ)
> require 17 or more entries, causing a slab-out-of-bounds write in the
> kmalloc-4k slab.
>
> The maximum possible entry count is:
> tunnel(2) + eth(4) + VLAN(4) + IPv6_NAT(10) + redirect(1) = 21
>
> Increase NF_FLOW_RULE_ACTION_MAX to 24 (with headroom) to cover the
> worst case.
For the record, proposed patch:
https://patchwork.ozlabs.org/project/netfilter-devel/patch/20260326200935.729750-1-pablo@netfilter.org/
prev parent reply other threads:[~2026-03-26 21:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-07 17:23 [PATCH net] netfilter: nf_flow_table_offload: fix heap overflow in flow_action_entry_next() Hyunwoo Kim
2026-03-07 19:04 ` Florian Westphal
2026-03-16 10:53 ` Florian Westphal
2026-03-16 11:23 ` Hyunwoo Kim
2026-03-16 11:31 ` Hyunwoo Kim
2026-03-16 11:48 ` Florian Westphal
2026-03-16 11:56 ` Pablo Neira Ayuso
2026-03-16 14:17 ` Hyunwoo Kim
2026-03-16 14:58 ` Florian Westphal
2026-03-25 14:27 ` Florian Westphal
2026-03-25 15:18 ` Pablo Neira Ayuso
2026-03-08 10:41 ` Pablo Neira Ayuso
2026-03-26 21:32 ` Pablo Neira Ayuso [this message]
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