From 8a4613f01f5bb850cab34e3db572d97251d997b3 Mon Sep 17 00:00:00 2001 From: Luiz Fernando Capitulino Date: Mon, 28 Nov 2005 19:16:07 -0200 Subject: [PATCH] [PATCH] USB: usbserial: race-condition fix. There is a race-condition in usb-serial driver that can be triggered if a processes does 'port->tty->driver_data = NULL' in serial_close() while other processes is in kernel-space about to call serial_ioctl() on the same port. This happens because a process can open the device while there is another one closing it. The patch below fixes that by adding a semaphore to ensure that no process will open the device while another process is closing it. Note that we can't use spinlocks here, since serial_open() and serial_close() can sleep. Signed-off-by: Luiz Capitulino Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/usb-serial.c | 14 +++++++++++++- drivers/usb/serial/usb-serial.h | 4 ++++ 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c index 5bc023c73893..8bc8337c99c4 100644 --- a/drivers/usb/serial/usb-serial.c +++ b/drivers/usb/serial/usb-serial.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include "usb-serial.h" #include "pl2303.h" @@ -190,6 +191,9 @@ static int serial_open (struct tty_struct *tty, struct file * filp) port = serial->port[portNumber]; if (!port) return -ENODEV; + + if (down_interruptible(&port->sem)) + return -ERESTARTSYS; ++port->open_count; @@ -215,6 +219,7 @@ static int serial_open (struct tty_struct *tty, struct file * filp) goto bailout_module_put; } + up(&port->sem); return 0; bailout_module_put: @@ -222,6 +227,7 @@ bailout_module_put: bailout_kref_put: kref_put(&serial->kref, destroy_serial); port->open_count = 0; + up(&port->sem); return retval; } @@ -234,8 +240,10 @@ static void serial_close(struct tty_struct *tty, struct file * filp) dbg("%s - port %d", __FUNCTION__, port->number); + down(&port->sem); + if (port->open_count == 0) - return; + goto out; --port->open_count; if (port->open_count == 0) { @@ -253,6 +261,9 @@ static void serial_close(struct tty_struct *tty, struct file * filp) } kref_put(&port->serial->kref, destroy_serial); + +out: + up(&port->sem); } static int serial_write (struct tty_struct * tty, const unsigned char *buf, int count) @@ -774,6 +785,7 @@ int usb_serial_probe(struct usb_interface *interface, port->number = i + serial->minor; port->serial = serial; spin_lock_init(&port->lock); + sema_init(&port->sem, 1); INIT_WORK(&port->work, usb_serial_port_softint, port); serial->port[i] = port; } diff --git a/drivers/usb/serial/usb-serial.h b/drivers/usb/serial/usb-serial.h index 238a5a871ed6..d7d27c3385b3 100644 --- a/drivers/usb/serial/usb-serial.h +++ b/drivers/usb/serial/usb-serial.h @@ -16,6 +16,7 @@ #include #include +#include #define SERIAL_TTY_MAJOR 188 /* Nice legal number now */ #define SERIAL_TTY_MINORS 255 /* loads of devices :) */ @@ -30,6 +31,8 @@ * @serial: pointer back to the struct usb_serial owner of this port. * @tty: pointer to the corresponding tty for this port. * @lock: spinlock to grab when updating portions of this structure. + * @sem: semaphore used to synchronize serial_open() and serial_close() + * access for this port. * @number: the number of the port (the minor number). * @interrupt_in_buffer: pointer to the interrupt in buffer for this port. * @interrupt_in_urb: pointer to the interrupt in struct urb for this port. @@ -60,6 +63,7 @@ struct usb_serial_port { struct usb_serial * serial; struct tty_struct * tty; spinlock_t lock; + struct semaphore sem; unsigned char number; unsigned char * interrupt_in_buffer; -- 2.20.1