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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df3ae73eb9sm3264875ad.44.2026.09.19.14.52.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:52:42 -0700 (PDT) From: Hui Peng To: pablo@netfilter.org, fw@strlen.de, phil@nwl.cc, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] netfilter: nf_nat: fix unsigned range_size underflow for ICMP and GRE when max < min Date: Sat, 19 Sep 2026 21:52:42 +0000 Message-ID: <20260919215242.3471883-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In nf_nat_l4proto_unique_tuple(), when NF_NAT_RANGE_PROTO_SPECIFIED is set for IPPROTO_ICMP, IPPROTO_ICMPV6, or IPPROTO_GRE with max < min, computing max - min + 1 in a u16 range_size underflows (and wraps to 0 when min == max + 1, causing a divide-by-zero in % range_size for GRE). Handle max < min gracefully by swapping min and max for ICMP/ICMPv6 and clamping range_size to 1 for GRE, matching the TCP/UDP/SCTP path. Fixes: 203f2e78200c ("netfilter: nat: remove l4proto->unique_tuple") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index a4858c2b2d65..83f4eb63a584 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -575,8 +575,10 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, range_size = 65536; } else { min = ntohs(range->min_proto.icmp.id); - range_size = ntohs(range->max_proto.icmp.id) - - ntohs(range->min_proto.icmp.id) + 1; + max = ntohs(range->max_proto.icmp.id); + if (unlikely(max < min)) + swap(max, min); + range_size = max - min + 1; } goto find_free_id; #if IS_ENABLED(CONFIG_NF_CT_PROTO_GRE) @@ -596,7 +598,11 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, range_size = 65535; } else { min = ntohs(range->min_proto.gre.key); - range_size = ntohs(range->max_proto.gre.key) - min + 1; + max = ntohs(range->max_proto.gre.key); + if (max < min) + range_size = 1; + else + range_size = max - min + 1; } goto find_free_id; #endif