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SubjectRe: [PATCH] fix oops in usbserial_cleanup function;
On Fri, 15 Oct 2010 m00150988@huawei.com wrote:

> From:ma rui <m00150988@huawei.com>
> 1. I find this bug on OpenSUSE 11.3 which kernel version is 2.6.34, but the latest kernel version 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 version is 2.6.36-rc7
> c. After the dashboard has detected the device, I pull out the usb datacard
> d. Close dashboard,then kernel panic will happen in usbserial_clean function
>
> Yes, the datacard exit without close the port.
>
> But after the dashboard connect internet with hauwei datacard, then Hibernate/resume, the bug will happen too.
> Do you have any other good idea to resolve this bug,or please apply my patch,thanks. :)
>
>
> Signed-off-by: ma rui <m00150988@huawei.com>
>
>
> 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 2010-10-15 01:57:36.000000000 -0400
> @@ -328,6 +328,16 @@ static void serial_cleanup(struct tty_st
> /* The console is magical. Do not hang up the console hardware
> * or there will be tears.
> */
> + if (NULL == port)
> + return;
> + mutex_lock(&port->serial->disc_mutex);
> + if (port->serial->disconnected) {
> + return_serial(port->serial);
> + mutex_unlock(&port->serial->disc_mutex);
> + return;
> + }
> + mutex_unlock(&port->serial->disc_mutex);
> +
> if (port->port.console)
> return;

This patch is clearly wrong, since it skips some of the actions that
should be taken by serial_cleanup even if the port is already
disconnected.

Besides, the main point of the patch is to avoid problems when
port = tty->driver_data turns out to be NULL. But the only place where
tty->driver_data is set to NULL is further below in this same function!
So the problems should never arise.

If they do arise, it indicates there's a bug somewhere else. That
other bug can't be fixed by changing this function.

Alan Stern



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