Re: [PATCH v2] Bluetooth: btusb: fix memory leak on suspend and resume

Hi Vamshi,

kmemleak report:
unreferenced object 0xffff9b1127f00500 (size 208):
 comm "kworker/u17:2", pid 500, jiffies 4294937470 (age 580.136s)
 hex dump (first 32 bytes):
   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
   00 60 ed 05 11 9b ff ff 00 00 00 00 00 00 00 00  .`..............
 backtrace:
   [<000000006ab3fd59>] kmem_cache_alloc_node+0x17a/0x480
   [<0000000051a5f6f9>] __alloc_skb+0x5b/0x1d0
   [<0000000037e2d252>] hci_prepare_cmd+0x32/0xc0 [bluetooth]
   [<0000000010b586d5>] hci_req_add_ev+0x84/0xe0 [bluetooth]
   [<00000000d2deb520>] hci_req_clear_event_filter+0x42/0x70 [bluetooth]
   [<00000000f864bd8c>] hci_req_prepare_suspend+0x84/0x470 [bluetooth]
   [<000000001deb2cc4>] hci_prepare_suspend+0x31/0x40 [bluetooth]
   [<000000002677dd79>] process_one_work+0x209/0x3b0
   [<00000000aaa62b07>] worker_thread+0x34/0x400
   [<00000000826d176c>] kthread+0x126/0x140
   [<000000002305e558>] ret_from_fork+0x22/0x30
unreferenced object 0xffff9b1125c6ee00 (size 512):
 comm "kworker/u17:2", pid 500, jiffies 4294937470 (age 580.136s)
 hex dump (first 32 bytes):
   04 00 00 00 0d 00 00 00 05 0c 01 00 11 9b ff ff  ................
   00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
 backtrace:
   [<000000009f07c0cc>] slab_post_alloc_hook+0x59/0x270
   [<0000000049431dc2>] __kmalloc_node_track_caller+0x15f/0x330
   [<00000000027a42f6>] __kmalloc_reserve.isra.70+0x31/0x90
   [<00000000e8e3e76a>] __alloc_skb+0x87/0x1d0
   [<0000000037e2d252>] hci_prepare_cmd+0x32/0xc0 [bluetooth]
   [<0000000010b586d5>] hci_req_add_ev+0x84/0xe0 [bluetooth]
   [<00000000d2deb520>] hci_req_clear_event_filter+0x42/0x70 [bluetooth]
   [<00000000f864bd8c>] hci_req_prepare_suspend+0x84/0x470 [bluetooth]
   [<000000001deb2cc4>] hci_prepare_suspend+0x31/0x40 [bluetooth]
   [<000000002677dd79>] process_one_work+0x209/0x3b0
   [<00000000aaa62b07>] worker_thread+0x34/0x400
   [<00000000826d176c>] kthread+0x126/0x140
   [<000000002305e558>] ret_from_fork+0x22/0x30
unreferenced object 0xffff9b112b395788 (size 8):
 comm "kworker/u17:2", pid 500, jiffies 4294937470 (age 580.136s)
 hex dump (first 8 bytes):
   20 00 00 00 00 00 04 00                           .......
 backtrace:
   [<0000000052dc28d2>] kmem_cache_alloc_trace+0x15e/0x460
   [<0000000046147591>] alloc_ctrl_urb+0x52/0xe0 [btusb]
   [<00000000a2ed3e9e>] btusb_send_frame+0x91/0x100 [btusb]
   [<000000001e66030e>] hci_send_frame+0x7e/0xf0 [bluetooth]
   [<00000000bf6b7269>] hci_cmd_work+0xc5/0x130 [bluetooth]
   [<000000002677dd79>] process_one_work+0x209/0x3b0
   [<00000000aaa62b07>] worker_thread+0x34/0x400
   [<00000000826d176c>] kthread+0x126/0x140
   [<000000002305e558>] ret_from_fork+0x22/0x30

In pm sleep-resume context, while the btusb device rebinds, it enters
hci_unregister_dev(), whilst there is a possibility of hdev receiving
PM_POST_SUSPEND suspend_notifier event, leading to generation of msg
frames. When hci_unregister_dev() completes, i.e. hdev context is
destroyed/freed, those intermittently sent msg frames cause memory
leak.

BUG details:
Below is stack trace of thread that enters hci_unregister_dev(), marks
the hdev flag HCI_UNREGISTER to 1, and then goes onto to wait on notifier
lock - refer unregister_pm_notifier().

 hci_unregister_dev+0xa5/0x320 [bluetoot]
 btusb_disconnect+0x68/0x150 [btusb]
 usb_unbind_interface+0x77/0x250
 ? kernfs_remove_by_name_ns+0x75/0xa0
 device_release_driver_internal+0xfe/0x1
 device_release_driver+0x12/0x20
 bus_remove_device+0xe1/0x150
 device_del+0x192/0x3e0
 ? usb_remove_ep_devs+0x1f/0x30
 usb_disable_device+0x92/0x1b0
 usb_disconnect+0xc2/0x270
 hub_event+0x9f6/0x15d0
 ? rpm_idle+0x23/0x360
 ? rpm_idle+0x26b/0x360
 process_one_work+0x209/0x3b0
 worker_thread+0x34/0x400
 ? process_one_work+0x3b0/0x3b0
 kthread+0x126/0x140
 ? kthread_park+0x90/0x90
 ret_from_fork+0x22/0x30

Below is stack trace of thread executing hci_suspend_notifier() which
processes the PM_POST_SUSPEND event, while the unbinding thread is
waiting on lock.

 hci_suspend_notifier.cold.39+0x5/0x2b [bluetooth]
 blocking_notifier_call_chain+0x69/0x90
 pm_notifier_call_chain+0x1a/0x20
 pm_suspend.cold.9+0x334/0x352
 state_store+0x84/0xf0
 kobj_attr_store+0x12/0x20
 sysfs_kf_write+0x3b/0x40
 kernfs_fop_write+0xda/0x1c0
 vfs_write+0xbb/0x250
 ksys_write+0x61/0xe0
 __x64_sys_write+0x1a/0x20
 do_syscall_64+0x37/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix hci_suspend_notifer(), not to act on events when flag HCI_UNREGISTER
is set.

Signed-off-by: Vamshi K Sthambamkadi <redacted>
---
net/bluetooth/hci_core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel