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Sat, 07 Mar 2026 09:23:10 -0800 (PST) Received: from v4bel ([58.123.110.97]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c739dfbf4fesm4853022a12.0.2026.03.07.09.23.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Mar 2026 09:23:10 -0800 (PST) Date: Sun, 8 Mar 2026 02:23:06 +0900 From: Hyunwoo Kim To: pablo@netfilter.org, fw@strlen.de, phil@nwl.cc, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, imv4bel@gmail.com Subject: [PATCH net] netfilter: nf_flow_table_offload: fix heap overflow in flow_action_entry_next() Message-ID: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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. Fixes: efce49dfe6a8 ("netfilter: flowtable: add vlan pop action offload support") Signed-off-by: Hyunwoo Kim --- net/netfilter/nf_flow_table_offload.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c index 9b677e116487..e843f6d0355e 100644 --- a/net/netfilter/nf_flow_table_offload.c +++ b/net/netfilter/nf_flow_table_offload.c @@ -727,7 +727,7 @@ int nf_flow_rule_route_ipv6(struct net *net, struct flow_offload *flow, } EXPORT_SYMBOL_GPL(nf_flow_rule_route_ipv6); -#define NF_FLOW_RULE_ACTION_MAX 16 +#define NF_FLOW_RULE_ACTION_MAX 24 static struct nf_flow_rule * nf_flow_offload_rule_alloc(struct net *net, -- 2.43.0