In the Linux kernel, the following vulnerability has been resolved:

sctp: keep chunk->transport in step with the list it is queued on

__sctp_outq_flush_rtx() moves a gap-acked chunk onto another transport's
transmitted list without updating chunk->transport:

	if (chunk->tsn_gap_acked) {
		list_move_tail(&chunk->transmitted_list,
			       &transport->transmitted);
		continue;
	}

The chunk then sits on a live transport's list while chunk->transport still
names a different one.  If that transport is removed - sctp_assoc_rm_peer()
from an ASCONF Delete-IP - sctp_transport_free() RCU-frees it and the chunk
is left with a dangling pointer.  sctp_assoc_rm_peer() scrubs
peer->transmitted and asoc->outqueue.out_chunk_list, but the chunk is on
neither.

The pointer is not followed while tsn_gap_acked is set.  A SACK that
reneges on the TSN clears the flag, and the next SACK reaches

	tchunk->transport->flight_size -= sctp_data_size(tchunk);

inside the freed transport.  KASAN reports a slab-use-after-free read in
sctp_check_transmitted(), freed from sctp_assoc_rm_peer().  Both the
removal and the SACKs come from the association peer.

Set chunk->transport at the move.  The ordinary resend path needs nothing:
it reaches its list_move_tail() only after sctp_packet_append_chunk()
returned SCTP_XMIT_OK, and __sctp_packet_append_chunk() has rebound the
chunk by then.

Discovered by XBOW, triaged by Baul Lee <[email protected]>

https://git.kernel.org/stable/c/1adf929121e13e0b19200bb9fef715b918d483fe

https://git.kernel.org/stable/c/2b3b5eec8b2c30ee237e3c31a6a38de9c39d804d

https://git.kernel.org/stable/c/5ccf35ef0ed6059cdf8b1f4606a6584d5b67166b

https://git.kernel.org/stable/c/6575fb17230814b48b471727c8410c0aadff9274

https://git.kernel.org/stable/c/6b9e2ea2057113f3393990ba646d2d97c719a80d

https://git.kernel.org/stable/c/874a7c2b5e184f06134fdfde27e9ce9271bafe58

https://git.kernel.org/stable/c/9f2cf069a9a72a2d6b97ca8b4c70e714aac99749

https://git.kernel.org/stable/c/e2e7c1de0e226ca1b7fea2de57a6c9bca408709b

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