Fix the race condition between the following two flows that run in parallel: 1. l2cap_reassemble_sdu -> chan->ops->recv -> l2cap_sock_recv_cb -> __sock_queue_rcv_skb. 2. bt_sock_recvmsg -> skb_recv_datagram, skb_free_datagram. An SKB can be queued by the first flow and immediately dequeued and freed by the second flow, therefore the callers of l2cap_reassemble_sdu can't use the SKB after that function returns. However, some places continue accessing struct l2cap_ctrl that resides in the SKB's CB for a short time after l2cap_reassemble_sdu returns, leading to a use-after-free condition (the stack trace is below, line numbers for kernel 5.19.8). Fix it by keeping a local copy of struct l2cap_ctrl. BUG: KASAN: use-after-free in l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth Read of size 1 at addr ffff88812025f2f0 by task kworker/u17:3/43169 Workqueue: hci0 hci_rx_work [bluetooth] Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:107 (discriminator 4)) print_report.cold (mm/kasan/report.c:314 mm/kasan/report.c:429) ? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth kasan_report (mm/kasan/report.c:162 mm/kasan/report.c:493) ? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:6906) bluetooth l2cap_rx (net/bluetooth/l2cap_core.c:7236 net/bluetooth/l2cap_core.c:7271) bluetooth ? sk_filter_trim_cap (net/core/filter.c:123) ? l2cap_chan_hold_unless_zero (./arch/x86/include/asm/atomic.h:202 ./include/linux/atomic/atomic-instrumented.h:560 ./include/linux/refcount.h:157 ./include/linux/refcount.h:227 ./include/linux/refcount.h:245 ./include/linux/kref.h:111 net/bluetooth/l2cap_core.c:517) bluetooth ? l2cap_rx_state_recv (net/bluetooth/l2cap_core.c:7252) bluetooth l2cap_recv_frame (net/bluetooth/l2cap_core.c:7405 net/bluetooth/l2cap_core.c:7620 net/bluetooth/l2cap_core.c:7723) bluetooth ? lock_release (./include/trace/events/lock.h:69 kernel/locking/lockdep.c:5677) ? hci_rx_work (net/bluetooth/hci_core.c:3637 net/bluetooth/hci_core.c:3832) bluetooth ? reacquire_held_locks (kernel/locking/lockdep.c:5674) ? trace_contention_end (./include/trace/events/lock.h:122 ./include/trace/events/lock.h:122) ? l2cap_config_rsp.isra.0 (net/bluetooth/l2cap_core.c:7674) bluetooth ? hci_rx_work (./include/net/bluetooth/hci_core.h:1024 net/bluetooth/hci_core.c:3634 net/bluetooth/hci_core.c:3832) bluetooth ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5637) ? __mutex_unlock_slowpath (./arch/x86/include/asm/atomic64_64.h:190 ./include/linux/atomic/atomic-long.h:449 ./include/linux/atomic/atomic-instrumented.h:1790 kernel/locking/mutex.c:924) ? rcu_read_lock_sched_held (kernel/rcu/update.c:104 kernel/rcu/update.c:123) ? memcpy (mm/kasan/shadow.c:65 (discriminator 1)) ? l2cap_recv_frag (net/bluetooth/l2cap_core.c:8340) bluetooth l2cap_recv_acldata (net/bluetooth/l2cap_core.c:8486) bluetooth hci_rx_work (net/bluetooth/hci_core.c:3642 net/bluetooth/hci_core.c:3832) bluetooth process_one_work (kernel/workqueue.c:2289) ? lock_downgrade (kernel/locking/lockdep.c:5634) ? pwq_dec_nr_in_flight (kernel/workqueue.c:2184) ? rwlock_bug.part.0 (kernel/locking/spinlock_debug.c:113) worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437) ? __kthread_parkme (./arch/x86/include/asm/bitops.h:207 (discriminator 4) ./include/asm-generic/bitops/instrumented-non-atomic.h:135 (discriminator 4) kernel/kthread.c:270 (discriminator 4)) ? process_one_work (kernel/workqueue.c:2379) kthread (kernel/kthread.c:376) ? kthread_complete_and_exit (kernel/kthread.c:331) ret_from_fork (arch/x86/entry/entry_64.S:306) </TASK> Allocated by task 43169: kasan_save_stack (mm/kasan/common.c:39) __kasan_slab_alloc (mm/kasan/common.c:45 mm/kasan/common.c:436 mm/kasan/common.c:469) kmem_cache_alloc_node (mm/slab.h:750 mm/slub.c:3243 mm/slub.c:3293) __alloc_skb (net/core/skbuff.c:414) l2cap_recv_frag (./include/net/bluetooth/bluetooth.h:425 net/bluetooth/l2cap_core.c:8329) bluetooth l2cap_recv_acldata (net/bluetooth/l2cap_core.c:8442) bluetooth hci_rx_work (net/bluetooth/hci_core.c:3642 net/bluetooth/hci_core.c:3832) bluetooth process_one_work (kernel/workqueue.c:2289) worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437) kthread (kernel/kthread.c:376) ret_from_fork (arch/x86/entry/entry_64.S:306) Freed by task 27920: kasan_save_stack (mm/kasan/common.c:39) kasan_set_track (mm/kasan/common.c:45) kasan_set_free_info (mm/kasan/generic.c:372) ____kasan_slab_free (mm/kasan/common.c:368 mm/kasan/common.c:328) slab_free_freelist_hook (mm/slub.c:1780) kmem_cache_free (mm/slub.c:3536 mm/slub.c:3553) skb_free_datagram (./include/net/sock.h:1578 ./include/net/sock.h:1639 net/core/datagram.c:323) bt_sock_recvmsg (net/bluetooth/af_bluetooth.c:295) bluetooth l2cap_sock_recvmsg (net/bluetooth/l2cap_sock.c:1212) bluetooth sock_read_iter (net/socket.c:1087) new_sync_read (./include/linux/fs.h:2052 fs/read_write.c:401) vfs_read (fs/read_write.c:482) ksys_read (fs/read_write.c:620) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) Link: https://lore.kernel.org/linux-bluetooth/CAKErNvoqga1WcmoR3-0875esY6TVWFQDandbVZncSiuGPBQXLA@xxxxxxxxxxxxxx/T/#u Fixes: d2a7ac5d5d3a ("Bluetooth: Add the ERTM receive state machine") Fixes: 4b51dae96731 ("Bluetooth: Add streaming mode receive and incoming packet classifier") Signed-off-by: Maxim Mikityanskiy <maxtram95@xxxxxxxxx> --- net/bluetooth/l2cap_core.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 2c9de67daadc..ea0929458f45 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -6886,6 +6886,8 @@ static int l2cap_rx_state_recv(struct l2cap_chan *chan, case L2CAP_EV_RECV_IFRAME: switch (l2cap_classify_txseq(chan, control->txseq)) { case L2CAP_TXSEQ_EXPECTED: + struct l2cap_ctrl local_control; + l2cap_pass_to_tx(chan, control); if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) { @@ -6900,15 +6902,16 @@ static int l2cap_rx_state_recv(struct l2cap_chan *chan, chan->buffer_seq = chan->expected_tx_seq; skb_in_use = true; + local_control = *control; err = l2cap_reassemble_sdu(chan, skb, control); if (err) break; - if (control->final) { + if (local_control.final) { if (!test_and_clear_bit(CONN_REJ_ACT, &chan->conn_state)) { - control->final = 0; - l2cap_retransmit_all(chan, control); + local_control.final = 0; + l2cap_retransmit_all(chan, &local_control); l2cap_ertm_send(chan); } } @@ -7288,11 +7291,12 @@ static int l2cap_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, static int l2cap_stream_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, struct sk_buff *skb) { + u16 txseq = control->txseq; + BT_DBG("chan %p, control %p, skb %p, state %d", chan, control, skb, chan->rx_state); - if (l2cap_classify_txseq(chan, control->txseq) == - L2CAP_TXSEQ_EXPECTED) { + if (l2cap_classify_txseq(chan, txseq) == L2CAP_TXSEQ_EXPECTED) { l2cap_pass_to_tx(chan, control); BT_DBG("buffer_seq %u->%u", chan->buffer_seq, @@ -7315,8 +7319,8 @@ static int l2cap_stream_rx(struct l2cap_chan *chan, struct l2cap_ctrl *control, } } - chan->last_acked_seq = control->txseq; - chan->expected_tx_seq = __next_seq(chan, control->txseq); + chan->last_acked_seq = txseq; + chan->expected_tx_seq = __next_seq(chan, txseq); return 0; } -- 2.37.3
