linux-kernel - Re: [REGRESSION][BISECTED] 5.5-rc suspend/resume failure caused by patch a4f55d8b8c14 ("usb: hub: Check device descriptor before resusciation")

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: <Pine.LNX.4.44L0.2001231035250.1518-100000@iolanthe.rowland.org>
Date:   Thu, 23 Jan 2020 10:50:05 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Paul Zimmerman <pauldzim@...il.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Heinzelmann <heinzelmann.david@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [REGRESSION][BISECTED] 5.5-rc suspend/resume failure caused by
 patch a4f55d8b8c14 ("usb: hub: Check device descriptor before resusciation")

On Wed, 22 Jan 2020, Paul Zimmerman wrote:

> > Still, since there was no real connection change at the port, there's
> > no reason to call hub_port_connect_change() here.  Let's see if the
> > patch below fixes your problem.
> > 
> > Alan Stern
> > 
> > 
> > 
> > Index: usb-devel/drivers/usb/core/hub.c
> > ===================================================================
> > --- usb-devel.orig/drivers/usb/core/hub.c
> > +++ usb-devel/drivers/usb/core/hub.c
> > @@ -1216,11 +1216,6 @@ static void hub_activate(struct usb_hub
> >  #ifdef CONFIG_PM
> >  			udev->reset_resume = 1;
> >  #endif
> > -			/* Don't set the change_bits when the device
> > -			 * was powered off.
> > -			 */
> > -			if (test_bit(port1, hub->power_bits))
> > -				set_bit(port1, hub->change_bits);
> >  
> >  		} else {
> >  			/* The power session is gone; tell hub_wq */
> > 
> 
> I can confirm this fixes the issue for me, I did a couple dozen
> suspend/resume cycles without seeing a failure.
> 
> I see the code you removed was added by Lan Tianyu in commit
> ad493e5e5805 ("usb: add usb port auto power off mechanism"). I

No, not really.  The set_bit() call was added by me in a much earlier
commit (8808f00c7adf, merged in 2008).  Lan Tianyu merely added the
"if" test, so that set_bit() doesn't always get called.  Now with this
change, set_bit() never gets called.

> wonder if your patch would break that? I don't know what that is
> or how to test it.

While some code review by people who are familiar with this material 
wouldn't hurt, I don't think you need to worry about any additional 
testing.

> In any case:
> Tested-by: Paul Zimmerman <pauldzim@...il.com>

Thank you.  I'll submit the patch soon.

Alan Stern