sed-opal: allow using IOC_OPAL_SAVE for locking too

Usually when closing a crypto device (eg: dm-crypt with LUKS) the
volume key is not required, as it requires root privileges anyway, and
root can deny access to a disk in many ways regardless. Requiring the
volume key to lock the device is a peculiarity of the OPAL
specification.

Given we might already have saved the key if the user requested it via
the 'IOC_OPAL_SAVE' ioctl, we can use that key to lock the device if no
key was provided here and the locking range matches, and the user sets
the appropriate flag with 'IOC_OPAL_SAVE'. This allows integrating OPAL
with tools and libraries that are used to the common behaviour and do
not ask for the volume key when closing a device.

Callers can always pass a non-zero key and it will be used regardless,
as before.

Suggested-by: Štěpán Horáček <[email protected]>
Signed-off-by: Luca Boccassi <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Christian Brauner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: bluca

block/sed-opal.c

@@ -2437,6 +2437,44 @@ static int __opal_set_mbr_done(struct opal_dev *dev, struct opal_key *key)
 	return execute_steps(dev, mbrdone_step, ARRAY_SIZE(mbrdone_step));
 }
 
+static void opal_lock_check_for_saved_key(struct opal_dev *dev,
+			    struct opal_lock_unlock *lk_unlk)
+{
+	struct opal_suspend_data *iter;
+
+	if (lk_unlk->l_state != OPAL_LK ||
+			lk_unlk->session.opal_key.key_len > 0)
+		return;
+
+	/*
+	 * Usually when closing a crypto device (eg: dm-crypt with LUKS) the
+	 * volume key is not required, as it requires root privileges anyway,
+	 * and root can deny access to a disk in many ways regardless.
+	 * Requiring the volume key to lock the device is a peculiarity of the
+	 * OPAL specification. Given we might already have saved the key if
+	 * the user requested it via the 'IOC_OPAL_SAVE' ioctl, we can use
+	 * that key to lock the device if no key was provided here, the
+	 * locking range matches and the appropriate flag was passed with
+	 * 'IOC_OPAL_SAVE'.
+	 * This allows integrating OPAL with tools and libraries that are used
+	 * to the common behaviour and do not ask for the volume key when
+	 * closing a device.
+	 */
+	setup_opal_dev(dev);
+	list_for_each_entry(iter, &dev->unlk_lst, node) {
+		if ((iter->unlk.flags & OPAL_SAVE_FOR_LOCK) &&
+				iter->lr == lk_unlk->session.opal_key.lr &&
+				iter->unlk.session.opal_key.key_len > 0) {
+			lk_unlk->session.opal_key.key_len =
+				iter->unlk.session.opal_key.key_len;
+			memcpy(lk_unlk->session.opal_key.key,
+				iter->unlk.session.opal_key.key,
+				iter->unlk.session.opal_key.key_len);
+			break;
+		}
+	}
+}
+
 static int opal_lock_unlock(struct opal_dev *dev,
 			    struct opal_lock_unlock *lk_unlk)
 {
@@ -2446,6 +2484,7 @@ static int opal_lock_unlock(struct opal_dev *dev,
 		return -EINVAL;
 
 	mutex_lock(&dev->dev_lock);
+	opal_lock_check_for_saved_key(dev, lk_unlk);
 	ret = __opal_lock_unlock(dev, lk_unlk);
 	mutex_unlock(&dev->dev_lock);
 

include/uapi/linux/sed-opal.h

@@ -44,6 +44,11 @@ enum opal_lock_state {
 	OPAL_LK = 0x04, /* 0100 */
 };
 
+enum opal_lock_flags {
+	/* IOC_OPAL_SAVE will also store the provided key for locking */
+	OPAL_SAVE_FOR_LOCK = 0x01,
+};
+
 struct opal_key {
 	__u8 lr;
 	__u8 key_len;
@@ -76,7 +81,8 @@ struct opal_user_lr_setup {
 struct opal_lock_unlock {
 	struct opal_session_info session;
 	__u32 l_state;
-	__u8 __align[4];
+	__u16 flags;
+	__u8 __align[2];
 };
 
 struct opal_new_pw {