CVE-2022-49910

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 net/bluetooth/l2cap_core.c:7271) bluetooth

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)