Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  amt: send the relay's General Query directly from the receive path  An skb queued in a qdisc can outlive the tunnel it references through a raw pointer in skb->cb. For example, with igmp_qrv set to 1 on the relay a tunnel lives for 135s, so a netem delay of 180s on the amt device outlives it; when the tunnel expires and is freed, the subsequent dequeue triggers a use-after-free in amt_dev_xmit().    BUG: KASAN: slab-use-after-free in amt_dev_xmit+0x2763/0x2e20   Call Trace:    amt_dev_xmit+0x2763/0x2e20 [drivers/net/amt.c:1262]    dev_hard_start_xmit+0x22f/0x620    sch_direct_xmit+0x12e/0xac0    netem_dequeue+0x333/0xc50    net_tx_action+0x35c/0xa60  amt_send_igmp_gq() and amt_send_mld_gq() are only called from amt_request_handler(), inside the rcu_read_lock_bh() section of amt_rcv(). amt_request_handler() already has the tunnel the query is for: it found or created it inside that section. Queuing the query with dev_queue_xmit() only leads back into amt_dev_xmit(), which strips the Ethernet header and calls amt_send_membership_query() for that tunnel.  Make that call directly from the two senders instead, the same way amt_send_advertisement() transmits from the receive path. The query never waits in a qdisc, the tunnel is only dereferenced inside the RCU section that found or created it, and nothing is stored in skb->cb, so no lookup or refcount is needed. Remove the query branch of amt_dev_xmit(), amt_skb_cb() and struct amt_skb_cb, which have no users left.  Behaviour changes:  - The relay's own General Queries no longer pass through the amt    device's egress path: its qdisc, tc egress (clsact/tcx), the    netfilter egress hook and packet taps. They are still visible as    UDP on the underlay.  - A query that is sent successfully is no longer counted as    tx_dropped. The old query branch left through the unlock label,    which counted every sent query as dropped.  - A query that reaches amt_dev_xmit() on a relay from elsewhere,    such as a userspace querier, is now dropped at the IGMP/MLD type    switch. Before, it trusted whatever skb->cb held, and a NULL    tunnel hit the WARN_ON(1).

CVEs

• CVE-2026-98968