From: Marco Elver <elver@google.com> mainline inclusion from mainline-v7.2-rc1 commit b66774b48dd98f07254951f74ea6f513efe7ff8b category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16068 CVE: CVE-2026-53358 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- l2cap_chan_timeout() runs asynchronously and accesses chan->conn. If the connection is torn down while the timer is running or pending, chan->conn can be freed, leading to a use-after-free when the timer worker attempts to lock conn->lock: | BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline] | BUG: KASAN: slab-use-after-free in atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline] | BUG: KASAN: slab-use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:161 [inline] | BUG: KASAN: slab-use-after-free in mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318 | Write of size 8 at addr ffff8881298d9550 by task kworker/2:1/83 | | CPU: 2 UID: 0 PID: 83 Comm: kworker/2:1 Not tainted 7.1.0-rc6-next-20260601-dirty #6 PREEMPT(full) | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 | Workqueue: events l2cap_chan_timeout | Call Trace: | <TASK> | instrument_atomic_read_write include/linux/instrumented.h:112 [inline] | atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline] | __mutex_trylock_fast kernel/locking/mutex.c:161 [inline] | mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318 | l2cap_chan_timeout+0x5d/0x1b0 net/bluetooth/l2cap_core.c:422 | process_one_work kernel/workqueue.c:3326 [inline] | process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409 | worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490 | kthread+0x346/0x430 kernel/kthread.c:436 | ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158 | ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 | </TASK> | | Allocated by task 320: | l2cap_conn_add+0xa7/0x820 net/bluetooth/l2cap_core.c:7075 | l2cap_connect_cfm+0xdb/0xd70 net/bluetooth/l2cap_core.c:7452 | hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline] | hci_remote_features_evt+0x52f/0x9f0 net/bluetooth/hci_event.c:3760 | hci_event_func net/bluetooth/hci_event.c:7796 [inline] | hci_event_packet+0x561/0xa70 net/bluetooth/hci_event.c:7847 | hci_rx_work+0x370/0x890 net/bluetooth/hci_core.c:4040 | process_one_work kernel/workqueue.c:3326 [inline] | process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409 | worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490 | kthread+0x346/0x430 kernel/kthread.c:436 | ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158 | ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 | | Freed by task 322: | hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline] | hci_conn_hash_flush+0x101/0x1f0 net/bluetooth/hci_conn.c:2736 | hci_dev_close_sync+0x889/0xde0 net/bluetooth/hci_sync.c:5405 | hci_dev_do_close net/bluetooth/hci_core.c:502 [inline] | hci_unregister_dev+0x1f7/0x370 net/bluetooth/hci_core.c:2679 | vhci_release+0x12a/0x180 drivers/bluetooth/hci_vhci.c:690 | __fput+0x369/0x890 fs/file_table.c:510 | task_work_run+0x160/0x1d0 kernel/task_work.c:233 | get_signal+0xf5b/0x1120 kernel/signal.c:2810 | arch_do_signal_or_restart+0x4d/0x600 arch/x86/kernel/signal.c:337 | __exit_to_user_mode_loop kernel/entry/common.c:64 [inline] | exit_to_user_mode_loop+0x85/0x510 kernel/entry/common.c:98 | do_syscall_64+0x263/0x3d0 arch/x86/entry/syscall_64.c:100 | entry_SYSCALL_64_after_hwframe+0x77/0x7f | | The buggy address belongs to the object at ffff8881298d9400 | which belongs to the cache kmalloc-512 of size 512 | The buggy address is located 336 bytes inside of | freed 512-byte region [ffff8881298d9400, ffff8881298d9600) Fix it by having chan->conn hold a reference to l2cap_conn (via l2cap_conn_get) when the channel is added to the connection, and releasing it in the channel destructor. This ensures the l2cap_conn remains alive as long as the channel exists. A new FLAG_DEL channel flag is introduced to indicate that the channel has been deleted from its connection. l2cap_chan_del() atomically sets this flag using test_and_set_bit() instead of setting chan->conn to NULL. All asynchronous workers (l2cap_chan_timeout, l2cap_ack_timeout, l2cap_monitor_timeout, l2cap_retrans_timeout) and l2cap_chan_send() check FLAG_DEL to determine whether the channel has been torn down, rather than testing chan->conn for NULL. Fixes: 8c8e620467a7 ("Bluetooth: L2CAP: use chan timer to close channels in cleanup_listen()") Cc: <stable@vger.kernel.org> Cc: Siwei Zhang <oss@fourdim.xyz> Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com> Assisted-by: Gemini:gemini-3.1-pro-preview Reported-by: https://sashiko.dev/#/patchset/20260521021249.3258069-1-oss%40fourdim.xyz Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com> Signed-off-by: Chen Jinghuang <chenjinghuang2@huawei.com> --- include/net/bluetooth/l2cap.h | 1 + net/bluetooth/l2cap_core.c | 34 ++++++++++++++++++++-------------- 2 files changed, 21 insertions(+), 14 deletions(-) diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index bf23edb02838..2c0356e7b571 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -742,6 +742,7 @@ enum { FLAG_ECRED_CONN_REQ_SENT, FLAG_PENDING_SECURITY, FLAG_HOLD_HCI_CONN, + FLAG_DEL, }; /* Lock nesting levels for L2CAP channels. We need these because lockdep diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 8d5060c17219..5e951a1935e1 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -411,7 +411,7 @@ static void l2cap_chan_timeout(struct work_struct *work) BT_DBG("chan %p state %s", chan, state_to_string(chan->state)); - if (!conn) { + if (test_bit(FLAG_DEL, &chan->flags)) { l2cap_chan_put(chan); return; } @@ -422,6 +422,9 @@ static void l2cap_chan_timeout(struct work_struct *work) */ l2cap_chan_lock(chan); + if (test_bit(FLAG_DEL, &chan->flags)) + goto unlock; + if (chan->state == BT_CONNECTED || chan->state == BT_CONFIG) reason = ECONNREFUSED; else if (chan->state == BT_CONNECT && @@ -434,10 +437,10 @@ static void l2cap_chan_timeout(struct work_struct *work) chan->ops->close(chan); +unlock: l2cap_chan_unlock(chan); - l2cap_chan_put(chan); - mutex_unlock(&conn->lock); + l2cap_chan_put(chan); } struct l2cap_chan *l2cap_chan_create(void) @@ -490,6 +493,9 @@ static void l2cap_chan_destroy(struct kref *kref) list_del(&chan->global_l); write_unlock(&chan_list_lock); + if (chan->conn) + l2cap_conn_put(chan->conn); + kfree(chan); } @@ -593,7 +599,7 @@ void __l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan) conn->disc_reason = HCI_ERROR_REMOTE_USER_TERM; - chan->conn = conn; + chan->conn = l2cap_conn_get(conn); switch (chan->chan_type) { case L2CAP_CHAN_CONN_ORIENTED: @@ -648,30 +654,26 @@ void l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan) void l2cap_chan_del(struct l2cap_chan *chan, int err) { - struct l2cap_conn *conn = chan->conn; - __clear_chan_timer(chan); - BT_DBG("chan %p, conn %p, err %d, state %s", chan, conn, err, + BT_DBG("chan %p, err %d, state %s", chan, err, state_to_string(chan->state)); chan->ops->teardown(chan, err); - if (conn) { + if (!test_and_set_bit(FLAG_DEL, &chan->flags)) { /* Delete from channel list */ list_del(&chan->list); l2cap_chan_put(chan); - chan->conn = NULL; - /* Reference was only held for non-fixed channels or * fixed channels that explicitly requested it using the * FLAG_HOLD_HCI_CONN flag. */ if (chan->chan_type != L2CAP_CHAN_FIXED || test_bit(FLAG_HOLD_HCI_CONN, &chan->flags)) - hci_conn_drop(conn->hcon); + hci_conn_drop(chan->conn->hcon); } if (test_bit(CONF_NOT_COMPLETE, &chan->conf_state)) @@ -1886,7 +1888,7 @@ static void l2cap_monitor_timeout(struct work_struct *work) l2cap_chan_lock(chan); - if (!chan->conn) { + if (test_bit(FLAG_DEL, &chan->flags)) { l2cap_chan_unlock(chan); l2cap_chan_put(chan); return; @@ -1907,7 +1909,7 @@ static void l2cap_retrans_timeout(struct work_struct *work) l2cap_chan_lock(chan); - if (!chan->conn) { + if (test_bit(FLAG_DEL, &chan->flags)) { l2cap_chan_unlock(chan); l2cap_chan_put(chan); return; @@ -2522,7 +2524,7 @@ int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len) int err; struct sk_buff_head seg_queue; - if (!chan->conn) + if (test_bit(FLAG_DEL, &chan->flags)) return -ENOTCONN; /* Connectionless channel */ @@ -3108,12 +3110,16 @@ static void l2cap_ack_timeout(struct work_struct *work) l2cap_chan_lock(chan); + if (test_bit(FLAG_DEL, &chan->flags)) + goto unlock; + frames_to_ack = __seq_offset(chan, chan->buffer_seq, chan->last_acked_seq); if (frames_to_ack) l2cap_send_rr_or_rnr(chan, 0); +unlock: l2cap_chan_unlock(chan); l2cap_chan_put(chan); } -- 2.34.1