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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a023e44854sm1830886a91.4.2026.09.19.14.52.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:52:39 -0700 (PDT) From: Hui Peng To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, kuniyu@google.com, willemb@google.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] fou: reject FOU_ENCAP_DIRECT with protocol 0 to prevent sk_buff leak Date: Sat, 19 Sep 2026 21:52:38 +0000 Message-ID: <20260919215238.3471141-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In fou_udp_recv(), returning -fou->protocol to udp_queue_rcv_one_skb() triggers IP protocol resubmission when fou->protocol > 0, whereas returning 0 tells the UDP tunnel layer that the skb was consumed without freeing it. When a FOU_ENCAP_DIRECT socket is configured with FOU_ATTR_IPPROTO == 0, every received packet returns 0 from fou_udp_recv() and leaks the sk_buff. Reject FOU_ENCAP_DIRECT configurations with protocol 0 in parse_nl_config() and drop packets if !fou->protocol in fou_udp_recv(). Fixes: 08d323234d10 ("net: fou: rename the source for linking") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/net/ipv4/fou_core.c b/net/ipv4/fou_core.c index 5e867f1b5c1d..3fc087c808bc 100644 --- a/net/ipv4/fou_core.c +++ b/net/ipv4/fou_core.c @@ -77,6 +77,9 @@ static int fou_udp_recv(struct sock *sk, struct sk_buff *skb) if (!fou) return 1; + if (unlikely(!fou->protocol)) + goto drop; + if (fou_recv_pull(skb, fou, sizeof(struct udphdr))) goto drop; @@ -696,6 +699,9 @@ static int parse_nl_config(struct genl_info *info, if (info->attrs[FOU_ATTR_TYPE]) cfg->type = nla_get_u8(info->attrs[FOU_ATTR_TYPE]); + if (cfg->type == FOU_ENCAP_DIRECT && !cfg->protocol) + return -EINVAL; + if (info->attrs[FOU_ATTR_REMCSUM_NOPARTIAL]) cfg->flags |= FOU_F_REMCSUM_NOPARTIAL;