From 331879fd6f584d60327ba802616d41bfa636b873 Mon Sep 17 00:00:00 2001 From: James Woodcock Date: Wed, 11 Feb 2009 15:06:53 +0000 Subject: USB: serial: refuse to open recently removed USB Serial devices A USB-serial converter device is plugged into a system, and a process opens it's device node. If the device is physically removed whilst the process still has its device node open, then other processes can sucessfully open the now non-existent device's node. I would expect that open() on a device that has been physically removed should return ENODEV. This is manifesting itself with getty on my system. I do the following: 1. set up inittab to spawn getty on ttyUSB0, eg: T1:23:respawn:/sbin/getty -L ttyUSB0 115200 vt100 2. Plug in USB-serial converter cable 3. Wait for a login prompt on a terminal program attached to the serial cable 4. Login 5. Pull the USB-serial converter cable from the box 6. getty doesn't realise that ttyUSB0 no longer exists as /dev/ttyUSB0 can still be opened. 7. Re-insert the USB-serial converter cable 8. You should no longer get a login prompt over the serial cable, as the the USB-serial cable now shows up as /dev/ttyUSB1, and getty is trying to talk to /dev/ttyUSB0. The attached patch will cause open("/dev/ttyUSB0", O_RDONLY) to return ENODEV after the USB-serial converter has been pulled. The patch was created against 2.6.28.1. I can supply it against something else if needs be. It is fairly simple, so should be OK. I am using a pl2303 device, although I don't think that makes any difference. From: James Woodcock Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/usb-serial.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'drivers/usb/serial') diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c index 9a2617845dfc..73172898ccb3 100644 --- a/drivers/usb/serial/usb-serial.c +++ b/drivers/usb/serial/usb-serial.c @@ -204,6 +204,11 @@ static int serial_open (struct tty_struct *tty, struct file *filp) goto bailout_kref_put; } + if (port->serial->disconnected) { + retval = -ENODEV; + goto bailout_kref_put; + } + if (mutex_lock_interruptible(&port->mutex)) { retval = -ERESTARTSYS; goto bailout_kref_put; -- cgit v1.2.3