Memory (skb) leak in kernel 4.8-rc2

Memory (skb) leak in kernel 4.8-rc2

[Larry Finger]

I am seeing two skb leaks in the BT sub-system for kernel 4.8-rc2. I only 
recently re-enabled kmemleak, but I do not think I saw these leaks in 4.7.

The first leak is at btusb_recv_intr+0x12b/0x170 [btusb]. This address refers to 
the call to bt_skb_alloc() in routine btusb_recv_intr().

The second leak is at hci_event_packet+0xb8/0x30b0 [bluetooth]. The backtrace 
for this address is

0x13d38 is in hci_event_packet (net/bluetooth/hci_event.c:5254).
5249             * various handlers may modify the original one through
5250             * skb_pull() calls, etc.
5251             */
5252            if (req_complete_skb || event == HCI_EV_CMD_STATUS ||
5253                event == HCI_EV_CMD_COMPLETE)
5254                    orig_skb = skb_clone(skb, GFP_KERNEL);
5255
5256            skb_pull(skb, HCI_EVENT_HDR_SIZE);
5257
5258            switch (event) {

I am unable to unload module bluetooth to verify that the second leak is not a 
false positive; however, the one in btusb is a real memory leak.

As always, I will be happy to test any patches.

Larry

Re: Memory (skb) leak in kernel 4.8-rc2

[Marcel Holtmann]

Hi Larry,

> I am seeing two skb leaks in the BT sub-system for kernel 4.8-rc2. I only recently re-enabled kmemleak, but I do not think I saw these leaks in 4.7.
> 
> The first leak is at btusb_recv_intr+0x12b/0x170 [btusb]. This address refers to the call to bt_skb_alloc() in routine btusb_recv_intr().

do you have a backtrace for this one? Also which hardware is this?

> The second leak is at hci_event_packet+0xb8/0x30b0 [bluetooth]. The backtrace for this address is
> 
> 0x13d38 is in hci_event_packet (net/bluetooth/hci_event.c:5254).
> 5249             * various handlers may modify the original one through
> 5250             * skb_pull() calls, etc.
> 5251             */
> 5252            if (req_complete_skb || event == HCI_EV_CMD_STATUS ||
> 5253                event == HCI_EV_CMD_COMPLETE)
> 5254                    orig_skb = skb_clone(skb, GFP_KERNEL);
> 5255
> 5256            skb_pull(skb, HCI_EVENT_HDR_SIZE);
> 5257
> 5258            switch (event) {
> 
> I am unable to unload module bluetooth to verify that the second leak is not a false positive; however, the one in btusb is a real memory leak.

I can not see a leak. Maybe Johan has an idea.

Regards

Marcel

Re: Memory (skb) leak in kernel 4.8-rc2

[Johan Hedberg]

Hi Marcel,

On Sat, Aug 20, 2016, Marcel Holtmann wrote:
> > I am seeing two skb leaks in the BT sub-system for kernel 4.8-rc2. I
> > only recently re-enabled kmemleak, but I do not think I saw these
> > leaks in 4.7.
> > 
> > The first leak is at btusb_recv_intr+0x12b/0x170 [btusb]. This
> > address refers to the call to bt_skb_alloc() in routine
> > btusb_recv_intr().
> 
> do you have a backtrace for this one? Also which hardware is this?
> 
> > The second leak is at hci_event_packet+0xb8/0x30b0 [bluetooth]. The
> > backtrace for this address is
> > 
> > 0x13d38 is in hci_event_packet (net/bluetooth/hci_event.c:5254).
> > 5249             * various handlers may modify the original one through
> > 5250             * skb_pull() calls, etc.
> > 5251             */
> > 5252            if (req_complete_skb || event == HCI_EV_CMD_STATUS ||
> > 5253                event == HCI_EV_CMD_COMPLETE)
> > 5254                    orig_skb = skb_clone(skb, GFP_KERNEL);
> > 5255
> > 5256            skb_pull(skb, HCI_EVENT_HDR_SIZE);
> > 5257
> > 5258            switch (event) {
> > 
> > I am unable to unload module bluetooth to verify that the second
> > leak is not a false positive; however, the one in btusb is a real
> > memory leak.
> 
> I can not see a leak. Maybe Johan has an idea.

Unfortunately I don't have any ideas either - there is no exit path from
hci_event_packet() after orig_skb has been allocated that would not
result in kfree_skb(orig_skb) being called first.

Johan

Re: Memory (skb) leak in kernel 4.8-rc2

[Frederic Dalleau]

Hi Marcel, Johan,

>>> I am unable to unload module bluetooth to verify that the second
>>> leak is not a false positive; however, the one in btusb is a real
>>> memory leak.

There was a bugzilla last week with that backtrace: 
https://bugzilla.kernel.org/show_bug.cgi?id=120691

At the time, I was thinking that the leak could originate from one of 
the req_complete_skb callback, but which one?

And today that the issue has popped again, I found that 
hci_req_sync_complete references the skb in hdev->req_skb. It is called 
(via hci_req_run_skb) from either __hci_cmd_sync_ev which will pass the 
skb to the caller, or __hci_req_sync which leaks.

I have a patch on the grill.

Best Regards,
Frédéric

Re: Memory (skb) leak in kernel 4.8-rc2

[Larry Finger]

On 08/21/2016 07:09 AM, Frederic Dalleau wrote:
> Hi Marcel, Johan,
>
>>>> I am unable to unload module bluetooth to verify that the second
>>>> leak is not a false positive; however, the one in btusb is a real
>>>> memory leak.
>
> There was a bugzilla last week with that backtrace:
> https://bugzilla.kernel.org/show_bug.cgi?id=120691
>
> At the time, I was thinking that the leak could originate from one of the
> req_complete_skb callback, but which one?
>
> And today that the issue has popped again, I found that hci_req_sync_complete
> references the skb in hdev->req_skb. It is called (via hci_req_run_skb) from
> either __hci_cmd_sync_ev which will pass the skb to the caller, or
> __hci_req_sync which leaks.
>
> I have a patch on the grill.

Frédéric,

Any progress on this patch?

Thanks,

Larry

Re: Memory (skb) leak in kernel 4.8-rc2

[Frederic Dalleau]

Hi Larry,

On 24/08/2016 22:02, Larry Finger wrote:
> On 08/21/2016 07:09 AM, Frederic Dalleau wrote:
>>>>> I am unable to unload module bluetooth to verify that the second
>>>>> leak is not a false positive; however, the one in btusb is a real
>>>>> memory leak.

>> I have a patch on the grill.

> Any progress on this patch?

Yes, it is in bluetooth-stable.
http://marc.info/?l=linux-bluetooth&m=147205068529234&w=2

Regards
Fred

Re: Memory (skb) leak in kernel 4.8-rc2

[Larry Finger]

On 08/25/2016 01:22 AM, Frederic Dalleau wrote:
> Hi Larry,
>
> On 24/08/2016 22:02, Larry Finger wrote:
>> On 08/21/2016 07:09 AM, Frederic Dalleau wrote:
>>>>>> I am unable to unload module bluetooth to verify that the second
>>>>>> leak is not a false positive; however, the one in btusb is a real
>>>>>> memory leak.
>
>>> I have a patch on the grill.
>
>> Any progress on this patch?
>
> Yes, it is in bluetooth-stable.
> http://marc.info/?l=linux-bluetooth&m=147205068529234&w=2

Fred,

Thanks for the link. That patch fixes the leaks that I was seeing from 
bluetooth. It also seems to have fixed the leaks that were attributed to btusb. 
At least, none have shown up in my preliminary testing.

Larry

Re: Memory (skb) leak in kernel 4.8-rc2

[Larry Finger]

On 08/20/2016 01:01 AM, Marcel Holtmann wrote:
> Hi Larry,
>
> I can not see a leak. Maybe Johan has an idea.

Marcel and Johan,

The hardware in question is an Intel device with USB ID 8087:07dc, which is part 
of an Intel Wireless 7260.

The kmemleak backtraces for the two kinds of leaks are:

unreferenced object 0xffff8801e182e000 (size 1024):
   comm "hardirq", pid 0, jiffies 4312467853 (age 61.716s)
   hex dump (first 32 bytes):
     00 84 82 e1 01 88 ff ff 0e 04 01 10 20 00 20 00  ............ . .
     05 06 02 00 00 05 00 00 40 00 40 00 00 00 00 00  ........@.@.....
   backtrace:
     [<ffffffff8169ef8a>] kmemleak_alloc+0x4a/0xa0
     [<ffffffff811e9b18>] __kmalloc_node_track_caller+0x178/0x270
     [<ffffffff815acb41>] __kmalloc_reserve.isra.35+0x31/0x90
     [<ffffffff815aec3e>] __alloc_skb+0x7e/0x280
     [<ffffffffa04c54bb>] btusb_recv_intr+0x12b/0x170 [btusb]
     [<ffffffffa04c55c5>] btusb_intr_complete+0xc5/0x130 [btusb]
     [<ffffffffa00a6f45>] __usb_hcd_giveback_urb+0x85/0x110 [usbcore]
     [<ffffffffa00a70df>] usb_hcd_giveback_urb+0x3f/0x130 [usbcore]
     [<ffffffffa0163cfa>] handle_tx_event+0x4ca/0x13c0 [xhci_hcd]
     [<ffffffffa0164e62>] xhci_irq+0x272/0xa30 [xhci_hcd]
     [<ffffffffa0165631>] xhci_msi_irq+0x11/0x20 [xhci_hcd]
     [<ffffffff810cb42f>] __handle_irq_event_percpu+0x3f/0x1d0
     [<ffffffff810cb5e3>] handle_irq_event_percpu+0x23/0x60
     [<ffffffff810cb65c>] handle_irq_event+0x3c/0x60
     [<ffffffff810ced0b>] handle_edge_irq+0x9b/0x160
     [<ffffffff8101e340>] handle_irq+0x20/0x30

unreferenced object 0xffff88010ccbd200 (size 256):
   comm "kworker/u17:2", pid 684, jiffies 4312467853 (age 61.716s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     1e c6 5f 75 10 90 6c 14 00 00 00 00 00 00 00 00  .._u..l.........
   backtrace:
     [<ffffffff8169ef8a>] kmemleak_alloc+0x4a/0xa0
     [<ffffffff811e8364>] kmem_cache_alloc+0xc4/0x1f0
     [<ffffffff815b04ac>] skb_clone+0x4c/0xa0
     [<ffffffffa0550d08>] hci_event_packet+0xb8/0x30b0 [bluetooth]
     [<ffffffffa054126d>] hci_rx_work+0x18d/0x380 [bluetooth]
     [<ffffffff81089f3b>] process_one_work+0x14b/0x430
     [<ffffffff8108a34b>] worker_thread+0x12b/0x490
     [<ffffffff8108fd49>] kthread+0xc9/0xe0
     [<ffffffff816a8e5f>] ret_from_fork+0x1f/0x40
     [<ffffffffffffffff>] 0xffffffffffffffff

I will attempt a bisection.

Larry