linux-kernel - Re: [RFT PATCH] xhci: Fix memory leak when caching protocol extended capability PSI tables

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Date:   Wed, 8 Jan 2020 17:56:50 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     pmenzel@...gen.mpg.de, mika.westerberg@...ux.intel.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH] xhci: Fix memory leak when caching protocol extended
 capability PSI tables

On 8.1.2020 17.40, Greg KH wrote:
> On Wed, Jan 08, 2020 at 05:17:30PM +0200, Mathias Nyman wrote:
>> xhci driver assumed that xHC controllers have at most one custom
>> supported speed table (PSI) for all usb 3.x ports.
>> Memory was allocated for one PSI table under the xhci hub structure.
>>
>> Turns out this is not the case, some controllers have a separate
>> "supported protocol capability" entry with a PSI table for each port.
>> This means each usb3 port can in theory support different custom speeds.
> 
> Is there a "max" number of port capabilities that can happen?  Or this
> this truely dynamic?

Almost truly dynamic, each capability points to the next, last points to 0

But we can't have more "supported protocol capabilities" than xHC ports.
(MaxPorts value in xHC HCSPARAMS1 register)

> 
>> +	for (i = 0; i < xhci->num_port_caps; i++) {
>> +		kfree(xhci->port_caps[i].psi);
>> +		xhci->port_caps[i].psi = NULL;
>> +	}
> 
> Nit, no need to set to NULL here :)

Thanks, will remove that

-Mathias