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

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Message-ID: <dd63c403-f35e-2543-e5ba-af40b263ea75@collabora.co.uk>
Date:   Sun, 21 Aug 2016 14:09:58 +0200
From:   Frederic Dalleau <frederic.dalleau@...labora.co.uk>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Larry Finger <Larry.Finger@...inger.net>,
        "Gustavo F. Padovan" <gustavo@...ovan.org>,
        Linux Bluetooth mailing list 
        <linux-bluetooth@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Memory (skb) leak in kernel 4.8-rc2

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