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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-sctp@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net] sctp: re-point retained control chunks on association migration Date: Thu, 30 Jul 2026 17:05:25 +0800 Message-ID: <20260730090537.27629-1-juny24602@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jun Yang sctp_control_set_owner_w() records the owning socket in a control chunk's skb->sk as a bare pointer. sctp_sock_migrate() re-owns the association's DATA chunks via sctp_for_each_tx_datachunk(), but that walk keys off chunk->msg and so skips control chunks: any control chunk the association still holds (for example the saved stream-reset request asoc->strreset_chunk, the ASCONF request/ack lists, or asoc->addip_last_asconf) keeps pointing at the old socket after the association is moved to the new one. Once the old socket is freed, a later retransmit reaches sctp_packet_transmit() -> skb_set_owner_w(head, chunk->skb->sk) and operates on the freed socket -- refcount_add() on its sk_wmem_alloc, then sk->sk_write_space() from sock_wfree() -- a use-after-free of struct sock. Re-point every control chunk the association still holds at the new socket right after sctp_assoc_migrate(), as is already done for DATA chunks. Control chunks carry no socket wmem charge and their skb destructor does not use skb->sk, so a bare owner update is sufficient. Fixes: d04adf1b3551 ("sctp: reset owner sk for data chunks on out queues when migrating a sock") Cc: stable@kernel.org Reported-by: TencentOS Corvus AI Signed-off-by: Jun Yang --- net/sctp/socket.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index c7b9e325ec1c..9a6da4e0d741 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -9522,6 +9522,30 @@ static void sctp_skb_set_owner_r_frag(struct sk_buff *skb, struct sock *sk) sctp_skb_set_owner_r(skb, sk); } +/* Control chunks record their owning socket in skb->sk as a bare pointer and + * are not reached by sctp_for_each_tx_datachunk(); re-point the ones the + * association still holds so migration does not leave them on the old socket. + */ +static void sctp_ctrl_set_owner_w(struct sctp_chunk *chunk, struct sock *sk) +{ + if (chunk && chunk->skb) + chunk->skb->sk = sk; +} + +static void sctp_for_each_tx_ctrlchunk(struct sctp_association *assoc, struct sock *sk) +{ + struct sctp_chunk *chunk; + + list_for_each_entry(chunk, &assoc->outqueue.control_chunk_list, list) + sctp_ctrl_set_owner_w(chunk, sk); + list_for_each_entry(chunk, &assoc->asconf_ack_list, transmitted_list) + sctp_ctrl_set_owner_w(chunk, sk); + list_for_each_entry(chunk, &assoc->addip_chunk_list, list) + sctp_ctrl_set_owner_w(chunk, sk); + sctp_ctrl_set_owner_w(assoc->strreset_chunk, sk); + sctp_ctrl_set_owner_w(assoc->addip_last_asconf, sk); +} + /* Populate the fields of the newsk from the oldsk and migrate the assoc * and its messages to the newsk. */ @@ -9633,6 +9657,7 @@ static int sctp_sock_migrate(struct sock *oldsk, struct sock *newsk, sctp_for_each_tx_datachunk(assoc, true, sctp_clear_owner_w); sctp_assoc_migrate(assoc, newsk); sctp_for_each_tx_datachunk(assoc, false, sctp_set_owner_w); + sctp_for_each_tx_ctrlchunk(assoc, newsk); /* If the association on the newsk is already closed before accept() * is called, set RCV_SHUTDOWN flag. -- 2.55.0