CVE-2022-49910 — Bluetooth: L2CAP: Fix use-after-free caused by l2cap_reassemble_sdu

Affected: Linux

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

Bluetooth: L2CAP: Fix use-after-free caused by l2cap_reassemble_sdu

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 ne…

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CVE-2022-49910 — Bluetooth: L2CAP: Fix use-after-free caused by l2cap_reassemble_sdu