moxa: prevent opening unavailable ports

In moxa.c there are 32 minor numbers reserved for each device. The
number of ports actually available per device is stored in
moxa_board_conf->numPorts. This number is not considered in moxa_open().
Opening a port that is not available results in a kernel oops.
This patch adds a test to moxa_open() that prevents opening unavailable
ports.

Signed-off-by: Dirk Eibach <eibach@gdsys.de>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/char/moxa.c b/drivers/char/moxa.c
index 4a4cab73d0be..65b6ff2442c6 100644
--- a/drivers/char/moxa.c
+++ b/drivers/char/moxa.c
@@ -1184,6 +1184,11 @@ static int moxa_open(struct tty_struct *tty, struct file *filp)
                 return -ENODEV;
         }
 
+        if (port % MAX_PORTS_PER_BOARD >= brd->numPorts) {
+                mutex_unlock(&moxa_openlock);
+                return -ENODEV;
+        }
+
         ch = &brd->ports[port % MAX_PORTS_PER_BOARD];
         ch->port.count++;
         tty->driver_data = ch;