From f4845ab191a4f686a5da481fbba90ed73bb693b0 Mon Sep 17 00:00:00 2001 From: Chengfeng Ye Date: Sun, 27 Sep 2026 01:04:02 +0800 Subject: [PATCH] Bluetooth: hci_core: Serialize ACL scheduling with channel deletion hci_chan_sent() selects a channel under RCU but drops the read lock before accessing chan->conn and returning the channel. The ACL and LE schedulers then use its packet queue and update its transmit counters without any protection against channel deletion. After TX selects a channel and releases RCU, a disconnect command timeout on the separate request workqueue can run hci_conn_failed() and l2cap_conn_del(). hci_chan_del() can then unlink the channel, complete synchronize_rcu(), purge its queue and free it before TX resumes. This causes use-after-free both in hci_chan_sent() and in its callers. KASAN reported: BUG: KASAN: slab-use-after-free in hci_chan_sent+0x892/0x9b0 Workqueue: hci0 hci_tx_work Call Trace: hci_chan_sent+0x892/0x9b0 hci_tx_work+0x5e6/0xb70 Allocated by task 91: hci_chan_create+0xe3/0x350 l2cap_conn_add.part.0+0x12/0xa30 l2cap_chan_connect+0x110d/0x1b60 l2cap_sock_connect+0x310/0x530 Freed by task 99: hci_chan_del+0x11f/0x170 l2cap_conn_del+0x4f1/0x800 l2cap_connect_cfm+0x88c/0xd30 hci_conn_failed+0x150/0x250 hci_abort_conn_sync+0x3e3/0x800 hci_cmd_sync_run+0x7e/0xc0 hci_abort_conn+0x105/0x1f0 disconnect_sync+0x157/0x290 hci_cmd_sync_work+0x13c/0x290 Hold the existing device mutex across channel selection and transmission in both schedulers to serialize them with channel teardown. Keep timeout handling outside the critical sections because hci_link_tx_to() acquires the same mutex. This also permits the transmit path to sleep, unlike extending the RCU read-side critical section across packet submission. Fixes: 3eff45eaf817 ("Bluetooth: convert tx_task to workqueue") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/hci_core.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c index bc662e24a8e4..a92ab4db4676 100644 --- a/net/bluetooth/hci_core.c +++ b/net/bluetooth/hci_core.c @@ -3675,6 +3675,8 @@ static void hci_sched_acl_pkt(struct hci_dev *hdev) __check_timeout(hdev, cnt, ACL_LINK); + hci_dev_lock(hdev); + while (hdev->acl_cnt && (chan = hci_chan_sent(hdev, ACL_LINK, "e))) { u32 priority = (skb_peek(&chan->data_q))->priority; @@ -3706,6 +3708,8 @@ static void hci_sched_acl_pkt(struct hci_dev *hdev) if (cnt != hdev->acl_cnt) hci_prio_recalculate(hdev, ACL_LINK); + + hci_dev_unlock(hdev); } static void hci_sched_acl(struct hci_dev *hdev) @@ -3734,6 +3738,8 @@ static void hci_sched_le(struct hci_dev *hdev) __check_timeout(hdev, *cnt, LE_LINK); + hci_dev_lock(hdev); + tmp = *cnt; while (*cnt && (chan = hci_chan_sent(hdev, LE_LINK, "e))) { u32 priority = (skb_peek(&chan->data_q))->priority; @@ -3762,6 +3768,8 @@ static void hci_sched_le(struct hci_dev *hdev) if (*cnt != tmp) hci_prio_recalculate(hdev, LE_LINK); + + hci_dev_unlock(hdev); } /* Schedule iso */