linux-kernel - Re: [RFC][PATCH v2 06/13] usb: hcd: Add hcd add/remove functions for OTG use

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5535F606.2070000@ti.com>
Date:	Tue, 21 Apr 2015 10:02:30 +0300
From:	Roger Quadros <rogerq@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Peter Chen <peter.chen@...escale.com>,
	<gregkh@...uxfoundation.org>, <balbi@...com>,
	<dan.j.williams@...el.com>, <jun.li@...escale.com>,
	<mathias.nyman@...ux.intel.com>, <tony@...mide.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [RFC][PATCH v2 06/13] usb: hcd: Add hcd add/remove functions
 for OTG use

On 20/04/15 16:56, Alan Stern wrote:
> On Mon, 20 Apr 2015, Roger Quadros wrote:
> 
>>> I don't understand this.  Why do you want to defer the add/remove if 
>>> the device is OTG?  Don't host controller drivers expect these things 
>>> to execute synchronously?
>>
>> Sorry for the wrong information. We actually defer only the add as the
>> OTG state machine might not yet be in Host ready mode.
>> The remove is always synchronous and we ensure that the HCD is removed
>> when usb_otg_unregister_hcd() returns.
> 
> That's okay then, but it does leave one potential hole.  What happens 
> if usb_add_hcd() is deferred for so long that usb_remove_hcd() gets 
> called before the add can complete?

We keep track of the HCD state in the OTG state machine and if it was not
yet added then _usb_remove_hcd() is not called during usb_otg_unregister_hcd()
in the usb_remove_hcd() call.

cheers,
-roger

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/