[PATCH v5 01/20] media: rc: Ensure registered is cleared in error path

[Sean Young <sean@mess.org>]

If rc_register_device() fails, ensure that registered is not set to true.
If lirc_register() succeeded, then userspace could have an open file
descriptor open. This leads to a use-after-free.

lirc_unregister() must be called with registered = false, else there is a
possibility that an fd is open and polling, which would never return
POLLERR unless registered is false.

Note that registered must be changed under dev->lock, many functions
read registered under lock (e.g. lirc_ioctl).

Fixes: dccc0c3ddf8f ("media: rc: fix race between unregister and urb/irq callbacks")
Signed-off-by: Sean Young <sean@mess.org>
Cc: stable@vger.kernel.org
---
 drivers/media/rc/rc-main.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c
index d93e98189c1a..930d45517229 100644
--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -1934,7 +1934,8 @@ int rc_register_device(struct rc_dev *dev)
 			goto out_raw;
 	}
 
-	dev->registered = true;
+	scoped_guard(mutex, &dev->lock)
+		dev->registered = true;
 
 	rc = device_add(&dev->dev);
 	if (rc)
@@ -1954,7 +1955,7 @@ int rc_register_device(struct rc_dev *dev)
 	if (dev->allowed_protocols != RC_PROTO_BIT_CEC) {
 		rc = lirc_register(dev);
 		if (rc < 0)
-			goto out_dev;
+			goto out_lirc;
 	}
 
 	if (dev->driver_type != RC_DRIVER_IR_RAW_TX) {
@@ -1977,11 +1978,18 @@ int rc_register_device(struct rc_dev *dev)
 out_rx:
 	rc_free_rx_device(dev);
 out_lirc:
-	if (dev->allowed_protocols != RC_PROTO_BIT_CEC)
+	scoped_guard(mutex, &dev->lock)
+		dev->registered = false;
+
+	if (device_is_registered(&dev->lirc_dev))
 		lirc_unregister(dev);
-out_dev:
 	device_del(&dev->dev);
+	/* registered already cleared above */
+	goto out_free_table;
 out_rx_free:
+	scoped_guard(mutex, &dev->lock)
+		dev->registered = false;
+out_free_table:
 	ir_free_table(&dev->rc_map);
 out_raw:
 	ida_free(&rc_ida, minor);
-- 
2.55.0