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Fri, 06 Nov 2026 10:52:11 -0800 (PST) Received: from localhost.localdomain ([14.116.239.35]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-85f1de8fdebsm2533411a34.25.2026.11.06.10.52.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2026 10:52:10 -0800 (PST) From: Henry Martin To: lucien.xin@gmail.com, marcelo.leitner@gmail.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, edumazet@kernel.org Cc: linux-sctp@vger.kernel.org, netdev@vger.kernel.org, Henry Martin , stable@vger.kernel.org Subject: [PATCH] sctp: fix skb_over_panic when adding addresses with a pending delete of another family Date: Sat, 7 Nov 2026 02:52:03 +0800 Message-ID: <20261106185203.3326303-1-bsdhenrymartin@gmail.com> X-Mailer: git-send-email 2.43.7 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit sctp_make_asconf_update_ip() accounts for a pending DEL_IP parameter by reusing the length of the address being added. The write-back side instead serializes the pending address itself, with its own address family. If the pending delete is IPv6 (20-byte parameter) while the added addresses are IPv4 (8-byte), the chunk is allocated 12 bytes short and sctp_addto_chunk() writes past the end of the skb. E.g. on mainline (05441d697f7f): skbuff: skb_over_panic: text:ffffffff84859c77 len:392 put:20 tail:0x188 end:0x180 dev: kernel BUG at net/core/skbuff.c:215! CPU: 0 UID: 1000 PID: 379 Comm: poc_sctp Call Trace: skb_panic skb_put sctp_addto_chunk sctp_make_asconf_update_ip sctp_send_asconf_add_ip sctp_setsockopt_bindx __x64_sys_setsockopt Requires addip enabled on the endpoint (net.sctp.addip_enable=1). Account for the pending delete with its own address family, as the write-back side already does. This issue was discovered by Tencent CodeBuddy Security. Cc: stable@vger.kernel.org Fixes: 8a07eb0a50ae ("sctp: Add ASCONF operation on the single-homed host") Signed-off-by: Henry Martin --- net/sctp/sm_make_chunk.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c index 90de272842512..18947ec5ff9f9 100644 --- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -2886,9 +2886,17 @@ struct sctp_chunk *sctp_make_asconf_update_ip(struct sctp_association *asoc, addr_buf += af->sockaddr_len; if (asoc->asconf_addr_del_pending && !del_pickup) { - /* reuse the parameter length from the same scope one */ + /* The DEL_IP parameter is serialized from the + * pending address itself below; account for its + * own address family, which may differ from the + * added one. + */ + addr = asoc->asconf_addr_del_pending; + af = sctp_get_af_specific(addr->v4.sin_family); + totallen += paramlen; - totallen += addr_param_len; + totallen += af->to_addr_param(addr, &addr_param); + del_pickup = 1; pr_debug("%s: picked same-scope del_pending addr, " -- 2.43.7