[PATCH v2 10/16] device-mapper: Refuse to create device named "control"

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

Typical userspace setups create a symlink under /dev/mapper with the
name of the device, but /dev/mapper/control is reserved for the control
device.  Therefore, trying to create such a device is almost certain to
be a userspace bug.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 drivers/md/dm-ioctl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 
52aa5505d23b2f3d9c0faf6e8a91b74cd7845581..9ae00e3c1a72c19575814cf473774835b364320b
 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -771,7 +771,12 @@ static int get_target_version(struct file *filp, struct 
dm_ioctl *param, size_t
 static int check_name(const char *name)
 {
        if (strchr(name, '/')) {
-               DMERR("invalid device name");
+               DMERR("device name cannot contain '/'");
+               return -EINVAL;
+       }
+
+       if (strcmp(name, DM_CONTROL_NODE) == 0) {
+               DMERR("device name cannot be \"%s\"", DM_CONTROL_NODE);
                return -EINVAL;
        }
 
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab