Patchwork [017/139] staging: comedi: disallow COMEDI_DEVCONFIG on non-board minors

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Submitter Luis Henriques
Date Feb. 28, 2013, 2:42 p.m.
Message ID <1362062689-2567-18-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/223993/
State New
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Luis Henriques - Feb. 28, 2013, 2:42 p.m.
3.5.7.7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Abbott <abbotti@mev.co.uk>

commit 754ab5c0e55dd118273ca2c217c4d95e9fbc8259 upstream.

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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/staging/comedi/comedi_fops.c | 5 +++++
 1 file changed, 5 insertions(+)

Patch

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index d231193..2831080 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -425,6 +425,11 @@  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)