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

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Date:	Tue, 26 Apr 2016 15:16:01 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	changbin.du@...el.com
Cc:	stern@...land.harvard.edu, baolu.lu@...ux.intel.com,
	chasemetzger15@...il.com, balbi@...com, kborer@...il.com,
	mjg59@...eos.com, jun.li@...escale.com, Robert.Schlabbach@....net,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	tonyb@...ernetics.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


> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 51b43691..27444e5 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -5401,7 +5401,6 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
>  	}
>  
>  	bos = udev->bos;
> -	udev->bos = NULL;
>  
>  	for (i = 0; i < SET_CONFIG_TRIES; ++i) {
>  
> @@ -5494,13 +5493,18 @@ done:
>  	usb_set_usb2_hardware_lpm(udev, 1);
>  	usb_unlocked_enable_lpm(udev);
>  	usb_enable_ltm(udev);
> -	usb_release_bos_descriptor(udev);
> -	udev->bos = bos;
> +	/* release the new BOS descriptor allocated by hub_port_init() */
> +	if (udev->bos != bos) {
> +		usb_release_bos_descriptor(udev);
> +		udev->bos = bos;
> +	}
>  	return 0;
>  
>  re_enumerate:
> -	usb_release_bos_descriptor(udev);
> -	udev->bos = bos;
> +	if (udev->bos != bos) {
> +		usb_release_bos_descriptor(udev);
> +		udev->bos = bos;
> +	}
>  re_enumerate_no_bos:
>  	/* LPM state doesn't matter when we're about to destroy the device. */
>  	hub_port_logical_disconnect(parent_hub, port1);
> -- 
> 2.5.0
> 
> --
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