In the Linux kernel, the following vulnerability has been resolved: mac802154: fix use-after-free of sdata via queued RX frames The RX softirq producer ieee802154_subif_frame() queues received beacon and MAC-command frames onto local->…

Overview

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

mac802154: fix use-after-free of sdata via queued RX frames

The RX softirq producer ieee802154_subif_frame() queues received beacon and MAC-command frames onto local->rx_beacon_list / rx_mac_cmd_list and schedules a process-context worker, storing a raw mac_pkt->sdata (and skb->dev == sdata->dev) with neither a reference nor any locking:

• the lists have no lock: the softirq producer list_add_tail()s while the mac_wq worker list_del()s, so sibling interfaces on the same phy corrupt the list;

• the workers dereference the interface after it may have been freed. mac802154_rx_mac_cmd_worker() touches mac_pkt->sdata directly, and mac802154_rx_beacon_worker() -> mac802154_process_beacon() dereferences skb->dev (== sdata->dev). Removing an interface frees its sdata (netdev_priv) while a queued frame still points at it, so a later worker run is a use-after-free.

Reproduced under KASAN by flooding a victim interface with MAC command frames and removing it (the beacon path is the same class via skb->dev):

BUG: KASAN: slab-use-after-free in mac802154_rx_mac_cmd_worker+0x463/0x630 [mac802154] Read of size 4 at addr ffff888002f9ea18 by task kworker/u8:1/31 Workqueue: phy0-mac-cmds mac802154_rx_mac_cmd_worker [mac802154] Call Trace: mac802154_rx_mac_cmd_worker+0x463/0x630 [mac802154] process_one_work+0x611/0xe80 worker_thread+0x52e/0xdc0 kthread+0x30c/0x630 ret_from_fork+0x2fd/0x3e0

Fix both lists together:

• add local->rx_lock and take it around every list access: the softirq producer (plain spin_lock, softirq context) and the workers and flush (spin_lock_bh, process context);

• pin the interface for the lifetime of a queued frame with netdev_hold()/netdev_put(), so the worker can safely dereference sdata / skb->dev even while the interface is being removed;

• dequeue under the lock at the head and loop-drain the whole list in the workers (they previously processed one frame per run and relied on a later enqueue to drain the rest);

• drop not-yet-started frames of an interface before it is unregistered, from ieee802154_if_remove() (after the RCU grace period) and from the ieee802154_remove_interfaces() loop -- the latter is the whole-phy teardown path, which does not go through ieee802154_if_remove().

An in-flight worker that already dequeued a frame keeps its own netdev reference; unregister_netdevice() then waits it out in netdev_run_todo(), which runs at rtnl_unlock() (rtnl released) and after the interface has been closed, so it does not pin rtnl. A worker blocked in an association TX only delays that one interface's unregister (the usual "waiting for %s to become free"), it does not hold rtnl. netdev_hold() is used for this reason instead of a cancel_work_sync() under rtnl, which would block on the worker's unbounded MLME TX wait via ieee802154_sync_queue().

The mac-command worker additionally skips processing for a stopped interface (ieee802154_sdata_running()), avoiding a needless association response during teardown.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.