[v4] Bluetooth: msft: fix slab-use-after-free in msft_do_close()

Dear Luiz, could you revert the v3 patch and apply this?

Fix the use-after-free bug in msft->data by tying the
msft->data lifectime to hdev.
Also, change msft_unregister() name to msft_release().

How msft is used after freed:

[use]
msft_do_close()
  msft = hdev->msft_data;
  if (!msft)                      ...(1) <- passed.
    return;
  mutex_lock(&msft->filter_lock); ...(4) <- used after freed.

[free]
msft_unregister()
  msft = hdev->msft_data;
  hdev->msft_data = NULL;         ...(2)
  kfree(msft);                    ...(3) <- msft is freed.

==================================================================
BUG: KASAN: slab-use-after-free in __mutex_lock_common kernel/locking/mutex.c:587 [inline]
BUG: KASAN: slab-use-after-free in __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752
Read of size 8 at addr ffff888106cbbca8 by task kworker/u5:2/309

CPU: 0 PID: 309 Comm: kworker/u5:2 Not tainted 6.9.0-rc5+ #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci4 hci_error_reset
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x140 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x191/0x560 mm/kasan/report.c:488
 kasan_report+0xe2/0x120 mm/kasan/report.c:601
 __asan_report_load8_noabort+0x18/0x20 mm/kasan/report_generic.c:381
 __mutex_lock_common kernel/locking/mutex.c:587 [inline]
 __mutex_lock+0x8f/0xc30 kernel/locking/mutex.c:752
 mutex_lock_nested+0x1f/0x30 kernel/locking/mutex.c:804
 msft_do_close+0x292/0x700 net/bluetooth/msft.c:694
 hci_dev_close_sync+0x906/0xf10 net/bluetooth/hci_sync.c:5168
 hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
 hci_error_reset+0x152/0x410 net/bluetooth/hci_core.c:1091
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x90f/0x1530 kernel/workqueue.c:3335
 worker_thread+0x926/0xe70 kernel/workqueue.c:3416
 kthread+0x2e3/0x380 kernel/kthread.c:388
 ret_from_fork+0x5c/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 7328:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x70 mm/kasan/common.c:68
 kasan_save_alloc_info+0x3c/0x50 mm/kasan/generic.c:565
 poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
 __kasan_kmalloc+0xa2/0xc0 mm/kasan/common.c:387
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 kmalloc_trace+0x20c/0x3e0 mm/slub.c:3997
 kmalloc include/linux/slab.h:628 [inline]
 kzalloc include/linux/slab.h:749 [inline]
 msft_register+0x66/0x1d0 net/bluetooth/msft.c:760
 hci_register_dev+0x85e/0x9a0 net/bluetooth/hci_core.c:2737
 __vhci_create_device drivers/bluetooth/hci_vhci.c:438 [inline]
 vhci_create_device+0x390/0x720 drivers/bluetooth/hci_vhci.c:480
 vhci_get_user drivers/bluetooth/hci_vhci.c:537 [inline]
 vhci_write+0x39b/0x460 drivers/bluetooth/hci_vhci.c:617
 call_write_iter include/linux/fs.h:2110 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x8eb/0xb50 fs/read_write.c:590
 ksys_write+0x106/0x1f0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x84/0xa0 fs/read_write.c:652
 x64_sys_call+0x271a/0x2ce0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x9c/0x130 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 7332:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x30/0x70 mm/kasan/common.c:68
 kasan_save_free_info+0x44/0x50 mm/kasan/generic.c:579
 poison_slab_object+0x11a/0x190 mm/kasan/common.c:240
 __kasan_slab_free+0x3b/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2106 [inline]
 slab_free mm/slub.c:4280 [inline]
 kfree+0x13c/0x330 mm/slub.c:4390
 msft_unregister+0x9d/0x120 net/bluetooth/msft.c:785
 hci_unregister_dev+0x1d9/0x520 net/bluetooth/hci_core.c:2771
 vhci_release+0x8c/0xe0 drivers/bluetooth/hci_vhci.c:674
 __fput+0x36f/0x750 fs/file_table.c:422
 ____fput+0x1e/0x30 fs/file_table.c:450
 task_work_run+0x1da/0x280 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x856/0x2210 kernel/exit.c:878
 do_group_exit+0x201/0x2c0 kernel/exit.c:1027
 get_signal+0x12ff/0x1380 kernel/signal.c:2911
 arch_do_signal_or_restart+0x3b/0x650 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xcc/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xa8/0x130 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff888106cbbc00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 168 bytes inside of
 freed 256-byte region [ffff888106cbbc00, ffff888106cbbd00)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106cba
head: order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ffffe0000840(slab|head|node=0|zone=2|lastcpupid=0x3fffff)
page_type: 0xffffffff()
raw: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10
raw: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000
head: 0017ffffe0000840 ffff888100042040 ffffea00042de590 ffffea00041b3e10
head: 0000000000000000 00000000000a000a 00000001ffffffff 0000000000000000
head: 0017ffffe0000001 ffffea00041b2e81 dead000000000122 00000000ffffffff
head: 0000000200000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888106cbbb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888106cbbc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888106cbbc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff888106cbbd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888106cbbd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Fixes: 5031ffcc79b8 ("Bluetooth: Keep MSFT ext info throughout a
hci_dev's life cycle")
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
---
v1 -> v2: Move BT_DBG after null checking in msft_data_hold_unless_zero().
v2 -> v3: Make a msft lifetime fit hdev.
v3 -> v4:
- Fix a defconfig build failure, adding a missing declaration for
  msft_release()
- Fix a wrong fixes tag.

 net/bluetooth/hci_core.c | 3 +--
 net/bluetooth/msft.c     | 2 +-
 net/bluetooth/msft.h     | 4 ++--
 3 files changed, 4 insertions(+), 5 deletions(-)