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 <abbotti@xxxxxxxxx>
---
Note: patch applies to Greg's "staging-next" and "staging-linus"
branches and also some "stable" kernels but I need to check which ones
it applies cleanly to and which ones it needs backporting to.
If it's not too late, it would be nice if it ends up in 3.8-rc.
---
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 b798e42..294db0e 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)
--
1.8.1.1
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