From 754ab5c0e55dd118273ca2c217c4d95e9fbc8259 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 28 Jan 2013 16:14:31 +0000 Subject: [PATCH] staging: comedi: disallow COMEDI_DEVCONFIG on non-board minors Comedi has two sorts of minor devices: (a) normal board minor devices in the range 0 to COMEDI_NUM_BOARD_MINORS-1 inclusive; and (b) special subdevice minor devices in the range COMEDI_NUM_BOARD_MINORS upwards that are used to open the same underlying comedi device as the normal board minor devices, but with non-default read and write subdevices for asynchronous commands. The special subdevice minor devices get created when a board supporting asynchronous commands is attached to a normal board minor device, and destroyed when the board is detached from the normal board minor device. One way to attach or detach a board is by using the COMEDI_DEVCONFIG ioctl. This should only be used on normal board minors as the special subdevice minors are too ephemeral. In particular, the change introduced in commit 7d3135af399e92cf4c9bbc5f86b6c140aab3b88c ("staging: comedi: prevent auto-unconfig of manually configured devices") breaks horribly for special subdevice minor devices. Since there's no legitimate use for the COMEDI_DEVCONFIG ioctl on a special subdevice minor device node, disallow it and return -ENOTTY. Signed-off-by: Ian Abbott Cc: stable Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index fa534fe4864b33..38e4fcb418c0f5 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1633,6 +1633,11 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd, /* Device config is special, because it must work on * an unconfigured device. */ if (cmd == COMEDI_DEVCONFIG) { + if (minor >= COMEDI_NUM_BOARD_MINORS) { + /* Device config not appropriate on non-board minors. */ + rc = -ENOTTY; + goto done; + } rc = do_devconfig_ioctl(dev, (struct comedi_devconfig __user *)arg); if (rc == 0)