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sctp: drop a chunk if its transport was removed

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sctp_rcv() resolves the transport once per packet and leaves it in
chunk->transport. The lookup reference, or the one sctp_add_backlog() takes
if the socket is owned by userspace, keeps it around until the chunk has
been processed.

An authenticated ASCONF DEL-IP can remove it in the meantime.
sctp_assoc_rm_peer() takes the transport out of the association and calls
sctp_transport_free(), which tags it dead and drops the reference the
association held. There is a window on both paths: the packet can sit on
the socket backlog, and on the direct path the lookup completes before
bh_lock_sock().

The DATA chunk in that packet puts the removed transport back into
asoc->peer.last_data_from. Once the packet is done that reference goes
away and the transport is freed by RCU, so the next delayed SACK carries
the pointer into the SACK chunk and sctp_outq_select_transport() reads the
freed transport's state.

Drop the chunk in sctp_inq_push(), next to the existing rcvr->dead check.
Both paths reach it with the association's socket lock held. The peer
retransmits it.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/aoUJHQmxL0LFIMCw@v4bel
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Hyunwoo Kim
2026-08-19 10:38:37 +09:00
committed by Jakub Kicinski
parent 25b863cd6d
commit 03a9d10ecf
1 changed files with 5 additions and 2 deletions
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7
net/sctp/inqueue.c
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@@ -71,8 +71,11 @@ void sctp_inq_free(struct sctp_inq *queue)
*/
void sctp_inq_push(struct sctp_inq *q, struct sctp_chunk *chunk)
{
/* Directly call the packet handling routine. */
if (chunk->rcvr->dead) {
/* Directly call the packet handling routine. Drop the chunk if the
* receiver or the transport it was looked up on is gone.
*/
if (chunk->rcvr->dead ||
(chunk->transport && chunk->transport->dead)) {
sctp_chunk_free(chunk);
return;
}