linux-kernel - Re: [PATCH] fix oops in usbserial

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Date:	Thu, 14 Oct 2010 21:20:43 -0700
From:	Greg KH <greg@...ah.com>
To:	marui <m00150988@...wei.com>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	zihan@...wei.com, Lin Lei <Lin.Lei@...wei.com>,
	Franko Fang <huananhu@...wei.com>, wangyeqi@...wei.com
Subject: Re: [PATCH] fix oops in usbserial_cleanup function;

On Fri, Oct 15, 2010 at 11:50:56AM +0800, marui wrote:
> 1. I find this bug on OpenSUSE 11.3 which kernel vesion is 2.6.34, but the latest kernel vesion 2.6.36-rc7 aslo have this bug. This patch is based on the kernel of 2.6.36-rc7.
> 2. Bug report:
>    a. Install huawei datacard dashboard on OpenSUSE 11.3
>    b. Plug in huawei datacard into OpenSUSE 11.3 which kernel verison is 2.6.36-rc7
>    c. After the dashboard has detected the device, I  pull out the usb datacard
>    d. close datashboard,then kernel panic will happen in usbserial_cleanup function. 

What does the "dashboard" program do?  Hold the port open?

> 3. fix the bug:
>    I find usbserial_cleanup should judge the usb device wheher has been disconnected firtly.
> 
> 
> diff -uprN -X linux-2.6.36-rc7-orig/Documentation/dontdiff linux-2.6.36-rc7-orig/drivers/usb/serial/usb-serial.c linux-2.6.36-rc7/drivers/usb/serial/usb-serial.c
> 
> --- linux-2.6.36-rc7_orig/drivers/usb/serial/usb-serial.c 2010-10-06 16:39:52.000000000 -0400
> +++ linux-2.6.36-rc7/drivers/usb/serial/usb-serial.c 2010-10-14 20:59:47.000000000 -0400
> @@ -328,6 +328,20 @@ static void serial_cleanup(struct tty_st
>   /* The console is magical.  Do not hang up the console hardware
>    * or there will be tears.
>    */
> +        dbg("%s start\n",__func__);
> +        if(NULL == port)
> +        {
> +            dbg("%s NULL == port\n",__func__);
> +            return;

We don't need to keep the dbg statements here, do we?

> +        }
> + mutex_lock(&port->serial->disc_mutex);
> + if (port->serial->disconnected)
> +        {
> +                dbg("%s port->serial->disconnected\n",__func__);
> +                return_serial(port->serial);
> +  return;

You can't return with a lock held.

> +        }
> + mutex_unlock(&port->serial->disc_mutex);
>   if (port->port.console)
>    return;

Your tabs and spaces got all mixed up, and it can't be applied.  Also, I
need a "Signed-off-by:" line to be able to accept it.  Care to read the
file Documentation/SubmittingPatches for how to format a patch so we can
take it?

Also, run the patch through scripts/checkpatch.pl and resolve the coding
style issues before resending please.

thanks,

greg k-h
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