linux-kernel - RE: [PATCH] usb: hub: fix panic caused by NULL bos pointer during reset device

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Date:	Wed, 27 Apr 2016 02:53:06 +0000
From:	"Du, Changbin" <changbin.du@...el.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
	"chasemetzger15@...il.com" <chasemetzger15@...il.com>,
	"balbi@...com" <balbi@...com>,
	"kborer@...il.com" <kborer@...il.com>,
	"mjg59@...eos.com" <mjg59@...eos.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"Robert.Schlabbach@....net" <Robert.Schlabbach@....net>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tonyb@...ernetics.com" <tonyb@...ernetics.com>,
	"joe.lawrence@...atus.com" <joe.lawrence@...atus.com>
Subject: RE: [PATCH] usb: hub: fix panic caused by NULL bos pointer during
 reset device

> On Tue, Mar 08, 2016 at 05:15:17PM +0800, changbin.du@...el.com wrote:
> > From: "Du, Changbin" <changbin.du@...el.com>
> >
> > This is a reworked patch based on reverted commit d8f00cd685f5 ("usb:
> > hub: do not clear BOS field during reset device").
> >
> > The privious one caused double mem-free if run to re_enumerate label.
> > New patch title changed to distinguish from old one. And I have tested
> > it with memory debugging options.
> >
> > In function usb_reset_and_verify_device, the old BOS descriptor may
> > still be used before allocating a new one. (usb_disable_lpm function
> > uses it under the situation that it fails at usb_disable_link_state.)
> > So we cannot set the udev->bos to NULL before that, just keep what it
> > was. It will be overwrite when allocating a new one.
> >
> > How to reproduce:
> > 1. connect one usb3 hub to xhci port.
> > 2. connect several lpm-capable super-speed usb disk to the hub.
> > 3. copy big files to the usb disks.
> > 4. disconnect the hub and repeat step 1-4.
> >
> > Crash log:
> > BUG: unable to handle kernel NULL pointer dereference at
> > 0000000000000010
> > IP: [<ffffffff8171f98d>] usb_enable_link_state+0x2d/0x2f0
> > Call Trace:
> > [<ffffffff8171ed5b>] ? usb_set_lpm_timeout+0x12b/0x140
> > [<ffffffff8171fcd1>] usb_enable_lpm+0x81/0xa0
> > [<ffffffff8171fdd8>] usb_disable_lpm+0xa8/0xc0
> > [<ffffffff8171fe1c>] usb_unlocked_disable_lpm+0x2c/0x50
> > [<ffffffff81723933>] usb_reset_and_verify_device+0xc3/0x710
> > [<ffffffff8172c4ed>] ? usb_sg_wait+0x13d/0x190
> > [<ffffffff81724743>] usb_reset_device+0x133/0x280
> > [<ffffffff8179ccd1>] usb_stor_port_reset+0x61/0x70
> > [<ffffffff8179cd68>] usb_stor_invoke_transport+0x88/0x520
> >
> > Signed-off-by: Du, Changbin <changbin.du@...el.com>
> > ---
> >  drivers/usb/core/hub.c | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> Is this patch still needed?  I thought we had some other fix in this
> area...
> 
> confused,
> 
> greg k-h
> 

Hi, Greg k-h,
Sorry for it confused you. This patch still need. This is same fix with
previous commit d8f00cd685f5 ("usb: hub: do not clear BOS field
during reset device"). But d8f00cd685f5 is buggy and reverted. This
new patch should be the final fix.

Best Regards,
Du, Changbin