linux-kernel - [PATCH v2 5/6] device-mapper: Refuse to create device named "control"

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Message-Id: <20230603145244.1538-6-demi@invisiblethingslab.com>
Date:   Sat,  3 Jun 2023 10:52:43 -0400
From:   Demi Marie Obenour <demi@...isiblethingslab.com>
To:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com
Cc:     Demi Marie Obenour <demi@...isiblethingslab.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/6] device-mapper: Refuse to create device named "control"

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@...isiblethingslab.com>
---
 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 7510afe237d979a5ee71afe87a20d49f631de1aa..5b647ab044e44b0c9d0961b5a336b41f50408f88 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -767,7 +767,12 @@ 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