linux-kernel - Re: [PATCH] usbip: usbip_host: fix bad unlock balance during stub

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Date:   Wed, 16 May 2018 08:03:10 -0600
From:   Shuah Khan <shuah@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     valentina.manea.m@...il.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH] usbip: usbip_host: fix bad unlock balance during
 stub_probe()

On 05/15/2018 11:49 PM, Greg KH wrote:
> On Tue, May 15, 2018 at 05:57:23PM -0600, Shuah Khan (Samsung OSG) wrote:
>> stub_probe() calls put_busid_priv() in an error path when device isn't
>> found in the busid_table. Fix it by making put_busid_priv() safe to be
>> called with null struct bus_id_priv pointer.
>>
>> This problem happens when "usbip bind" is run without loading usbip_host
>> driver and then running modprobe. The first failed bind attempt unbinds
>> the device from the original driver and when usbip_host is modprobed,
>> stub_probe() runs and doesn't find the device in its busid table and calls
>> put_busid_priv(0 with null bus_id_priv pointer.
>>
>> usbip-host 3-10.2: 3-10.2 is not in match_busid table...  skip!
>>
>> [  367.359679] =====================================
>> [  367.359681] WARNING: bad unlock balance detected!
>> [  367.359683] 4.17.0-rc4+ #5 Not tainted
>> [  367.359685] -------------------------------------
>> [  367.359688] modprobe/2768 is trying to release lock (
>> [  367.359689]
>> ==================================================================
>> [  367.359696] BUG: KASAN: null-ptr-deref in
>> print_unlock_imbalance_bug+0x99/0x110
>> [  367.359699] Read of size 8 at addr 0000000000000058 by task
>> modprobe/2768
> 
> Minor nit, no need to line-wrap this.
> 
>> [  367.359705] CPU: 4 PID: 2768 Comm: modprobe Not tainted 4.17.0-rc4+ #5
>>
>> Fixes: 22076557b07c ("usbip: usbip_host: fix NULL-ptr deref and
>> use-after-free errors") in usb-linus
> 
> Nor this, and the extra blank line isn't needed here either.  I'll fix
> it up by hand when I queue this up later today, thanks.
> 

Thanks. I will keep that in mind the next time.

thanks,
-- Shuah