Re: [PATCH] Bluetooth: Fix UAF for hci_chan

[Ziyang Xuan (William)]

> Hi,
> 
> la, 2023-10-07 kello 17:35 +0800, Ziyang Xuan kirjoitti:
>> Syzbot reports a UAF problem as follows:
>>
>> BUG: KASAN: slab-use-after-free in hci_send_acl+0x48/0xe70 net/bluetooth/hci_core.c:3231
>> ...
>> Call Trace:
>>  <TASK>
>>  __dump_stack lib/dump_stack.c:88 [inline]
>>  dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
>>  print_address_description mm/kasan/report.c:364 [inline]
>>  print_report+0x163/0x540 mm/kasan/report.c:475
>>  kasan_report+0x175/0x1b0 mm/kasan/report.c:588
>>  hci_send_acl+0x48/0xe70 net/bluetooth/hci_core.c:3231
>>  l2cap_send_conn_req net/bluetooth/l2cap_core.c:1286 [inline]
>>  l2cap_start_connection+0x465/0x620 net/bluetooth/l2cap_core.c:1514
>>  l2cap_conn_start+0xbf3/0x1130 net/bluetooth/l2cap_core.c:1661
>>  process_one_work kernel/workqueue.c:2630 [inline]
>>  process_scheduled_works+0x90f/0x1400 kernel/workqueue.c:2703
>>  worker_thread+0xa5f/0xff0 kernel/workqueue.c:2784
>>  kthread+0x2d3/0x370 kernel/kthread.c:388
>>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>>  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
>>  </TASK>
> 
> Note this looks like the same issue as in the following thread, where
> there's a suggestion from maintainer:
> 
> https://lore.kernel.org/linux-bluetooth/fd9c0f0eddb8a7d73e9797568dc3cf2bc9b8ad62.1696077070.git.pav@xxxxxx/T/#u
> 
> 
> Is it the same issue?

Yes, Thank you for your reminder.

I think use ida to make handle unique can solve the problem more easily.

I will rebase my patch.

Ziyang Xuan
> 
>>
>> Allocated by task 27110:
>>  kasan_save_stack mm/kasan/common.c:45 [inline]
>>  kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
>>  ____kasan_kmalloc mm/kasan/common.c:374 [inline]
>>  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:383
>>  kmalloc include/linux/slab.h:599 [inline]
>>  kzalloc include/linux/slab.h:720 [inline]
>>  hci_chan_create+0xc8/0x300 net/bluetooth/hci_conn.c:2714
>>  l2cap_conn_add+0x69/0xc10 net/bluetooth/l2cap_core.c:7841
>>  l2cap_chan_connect+0x61f/0xeb0 net/bluetooth/l2cap_core.c:8053
>>  bt_6lowpan_connect net/bluetooth/6lowpan.c:894 [inline]
>>  lowpan_control_write+0x55e/0x850 net/bluetooth/6lowpan.c:1129
>>  full_proxy_write+0x113/0x1c0 fs/debugfs/file.c:236
>>  vfs_write+0x286/0xaf0 fs/read_write.c:582
>>  ksys_write+0x1a0/0x2c0 fs/read_write.c:637
>>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>
>> Freed by task 5067:
>>  kasan_save_stack mm/kasan/common.c:45 [inline]
>>  kasan_set_track+0x4f/0x70 mm/kasan/common.c:52
>>  kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
>>  ____kasan_slab_free+0xd6/0x120 mm/kasan/common.c:236
>>  kasan_slab_free include/linux/kasan.h:164 [inline]
>>  slab_free_hook mm/slub.c:1800 [inline]
>>  slab_free_freelist_hook mm/slub.c:1826 [inline]
>>  slab_free mm/slub.c:3809 [inline]
>>  __kmem_cache_free+0x25f/0x3b0 mm/slub.c:3822
>>  hci_chan_list_flush net/bluetooth/hci_conn.c:2754 [inline]
>>  hci_conn_cleanup net/bluetooth/hci_conn.c:152 [inline]
>>  hci_conn_del+0x4f8/0xc40 net/bluetooth/hci_conn.c:1156
>>  hci_abort_conn_sync+0xa45/0xfe0
>>  hci_cmd_sync_work+0x228/0x400 net/bluetooth/hci_sync.c:306
>>  process_one_work kernel/workqueue.c:2630 [inline]
>>  process_scheduled_works+0x90f/0x1400 kernel/workqueue.c:2703
>>  worker_thread+0xa5f/0xff0 kernel/workqueue.c:2784
>>  kthread+0x2d3/0x370 kernel/kthread.c:388
>>  ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:147
>>  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
>>
>> There are two main reasons for this:
>> 1. In the case of hci_conn_add() concurrency, the handle of
>> hci_conn allocated through hci_conn_hash_alloc_unset() is not unique.
>> 2. The processes related to hci_abort_conn() and hci_connect_xxx()
>> can be concurrent, but the two processes lack synchronization.
>>
>> To fix this, use ida to manage the allocation of conn->handle, and
>> add the HCI_CONN_DISC flag to achieve synchronization between
>> hci_abort_conn() and hci_connect_xxx() related processes.
>>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>