mac802154_scan_worker() captures the scanning sub-interface once under RCU: sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(scan_req->wpan_dev); and then, after rcu_read_unlock() and outside the rtnl, keeps dereferencing sdata->dev: in the channel-change and restart failure traces, in mac802154_transmit_beacon_req() (skb->dev = sdata->dev) for active scans, in the final dev_dbg(), and in the end_scan mac802154_scan_cleanup_locked() path. Nothing keeps that netdev alive for the duration of the worker iteration. A concurrent teardown of the scanning interface -- userspace issuing NL802154_CMD_DEL_INTERFACE (ieee802154_if_remove() -> unregister_netdevice()), or a full PHY removal via ieee802154_unregister_hw() -> ieee802154_remove_interfaces() -- can run as soon as the worker drops the rtnl between its two short drv_set_channel()/drv_start() sections. The netdev is not freed synchronously by unregister_netdevice(): it is queued to net_todo_list and freed later from netdev_run_todo(), which drops the rtnl mutex (__rtnl_unlock()) *before* netdev_wait_allrefs_any()/free_netdev(). The freeing therefore runs with the rtnl not held, on whichever task next drains net_todo_list. Holding the rtnl in the worker does not prevent it, and the per-PHY IEEE802154_IS_SCANNING flag does not identify the specific interface: a subsequent NEW_INTERFACE + TRIGGER_SCAN re-arms the flag, so a stale worker iteration sails past an is-scanning recheck and dereferences the already-freed netdev. Triggering the race requires CAP_NET_ADMIN: both NL802154_CMD_TRIGGER_SCAN and NL802154_CMD_DEL_INTERFACE are GENL_ADMIN_PERM, reachable only from the initial user namespace, so the attacker is a locally privileged (CAP_NET_ADMIN) user, not an unprivileged local user or a remote peer. KASAN slab-use-after-free, kworker reading the freed net_device/ieee802154_sub_if_data (kmalloc-cg-4k) allocated and freed by the racing NEW_INTERFACE/DEL_INTERFACE task: BUG: KASAN: slab-use-after-free in mac802154_scan_worker+0x... [mac802154] Read of size 8 ... by task kworker/u8:N Workqueue: phy0-mac-cmds mac802154_scan_worker [mac802154] mac802154_scan_worker process_one_work (also hit via ieee802154_mlme_tx_locked() from the beacon-request path and via _dev_err()/__dev_printk() formatting sdata->dev->dev) Fix it by taking a reference on the interface while the RCU read lock is still held -- so the netdev cannot be freed before the refcount is raised -- and releasing it at every exit of the worker past that point. This keeps sdata->dev valid for the whole iteration. The reference does not defer the free indefinitely and does not deadlock the single-threaded mac_wq. Each worker iteration drops the reference before it requeues itself, and a teardown started while the reference is held simply blocks in netdev_run_todo() until the current iteration returns. It cannot be the worker's own rtnl_unlock() that blocks on the reference either: the unregistering task removes the netdev from net_todo_list under the rtnl (list_replace_init() in netdev_run_todo() runs before __rtnl_unlock()), so it always owns the todo entry, and the worker acquires the rtnl only afterwards -- the blocking netdev_wait_allrefs_any() therefore always runs on the teardown task, never on the worker. Verified on a v6.19 KASAN build: racing DEL_INTERFACE against an in-flight TRIGGER_SCAN reliably tripped a slab-use-after-free KASAN report inside mac802154_scan_worker() before this patch, and the same reproducer no longer triggers it with the fix applied. Fixes: 57588c71177f ("mac802154: Handle passive scanning") Cc: stable@vger.kernel.org Assisted-by: AuditCode-AI:2026.07 Signed-off-by: Ibrahim Hashimov --- net/mac802154/scan.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c index 0a31ac8d8415..48e661031cc0 100644 --- a/net/mac802154/scan.c +++ b/net/mac802154/scan.c @@ -209,6 +209,26 @@ void mac802154_scan_worker(struct work_struct *work) return; } + /* From here on sdata->dev is dereferenced after rcu_read_unlock() and + * outside the rtnl: in the dev_err()/dev_dbg() traces below, in + * mac802154_transmit_beacon_req() (skb->dev = sdata->dev) and in the + * end_scan mac802154_scan_cleanup_locked() call. A concurrent teardown + * of that interface (NL802154_CMD_DEL_INTERFACE -> + * ieee802154_if_remove(), or a full PHY removal via + * ieee802154_unregister_hw()) can unregister the netdev; the actual + * free then runs asynchronously from netdev_run_todo() with the rtnl + * already dropped, so neither holding the rtnl nor the per-PHY + * IEEE802154_IS_SCANNING flag keeps sdata->dev alive here. Pin it with + * a reference taken while we still hold the RCU read lock (so the + * netdev cannot be freed before we bump the refcount) and drop it at + * every exit below. This blocks the teardown's netdev_run_todo() until + * this worker iteration is done; it cannot self-deadlock because the + * unregistering task claims the net_todo_list entry under the rtnl, so + * the blocking netdev_wait_allrefs_any() always runs on that task, not + * on this single-threaded worker. + */ + dev_hold(sdata->dev); + wpan_phy = scan_req->wpan_phy; scan_req_type = scan_req->type; scan_req_duration = scan_req->duration; @@ -262,12 +282,14 @@ void mac802154_scan_worker(struct work_struct *work) "Scan page %u channel %u for %ums\n", page, channel, jiffies_to_msecs(scan_duration)); queue_delayed_work(local->mac_wq, &local->scan_work, scan_duration); + dev_put(sdata->dev); return; end_scan: rtnl_lock(); mac802154_scan_cleanup_locked(local, sdata, false); rtnl_unlock(); + dev_put(sdata->dev); } int mac802154_trigger_scan_locked(struct ieee802154_sub_if_data *sdata, -- 2.50.1 (Apple Git-155)