From: Jun Yang Date: Tue, 21 Jul 2026 13:14:05 +0000 (+0800) Subject: sctp: don't free the ASCONF's own transport in DEL-IP processing X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9b2854f86f0b56e9027d68e7a3fc909d1a9b566f;p=thirdparty%2Fkernel%2Flinux.git sctp: don't free the ASCONF's own transport in DEL-IP processing sctp_process_asconf() caches the transport the ASCONF chunk is processed against in asconf->transport (== chunk->transport, set once in sctp_rcv()). For an ASCONF located through its Address Parameter by __sctp_rcv_asconf_lookup(), that cached transport corresponds to the Address Parameter, which need not be the packet's source address. sctp_process_asconf_param() rejects a DEL-IP for the packet source address (ADDIP D8, SCTP_ERROR_DEL_SRC_IP), but nothing protects asconf->transport. A single ASCONF can therefore carry, in order: [Address Parameter L] [DEL-IP L] [DEL-IP 0.0.0.0] where L differs from the source. The DEL-IP for L passes the D8 check and calls sctp_assoc_rm_peer() on the transport that asconf->transport still points at, freeing it (RCU-deferred). The following wildcard DEL-IP then reuses the now-dangling asconf->transport in sctp_assoc_set_primary() and sctp_assoc_del_nonprimary_peers(): set_primary() dereferences the freed transport (->ipaddr, ->state) and plants the dangling pointer into asoc->peer.primary_path / active_path, and del_nonprimary_peers(), keeping only the pointer that is no longer on the list, removes every real transport, leaving the association with a transport_count of 0 and primary_path/active_path pointing at freed memory. Reject a DEL-IP that targets the transport the ASCONF is being processed against, mirroring the existing source-address guard, so the wildcard branch can never reuse a freed transport. Fixes: 42e30bf3463c ("[SCTP]: Handle the wildcard ADD-IP Address parameter") Cc: stable@kernel.org Signed-off-by: Jun Yang Acked-by: Xin Long Link: https://patch.msgid.link/tencent_73762ED1DF08CC9D5F5F61954B01350CFE0A@qq.com Signed-off-by: Jakub Kicinski --- diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c index 8adac9e0cd66..c02809264075 100644 --- a/net/sctp/sm_make_chunk.c +++ b/net/sctp/sm_make_chunk.c @@ -3153,6 +3153,12 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc, if (!peer) return SCTP_ERROR_DNS_FAILED; + /* Don't free asconf->transport; a later wildcard DEL-IP + * parameter reuses it. + */ + if (peer == asconf->transport) + return SCTP_ERROR_REQ_REFUSED; + sctp_assoc_rm_peer(asoc, peer); break; case SCTP_PARAM_SET_PRIMARY: