linux-kernel - [PATCH 4.11 095/150] [media] rc-core: race condition during ir_raw_event

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Date:   Mon, 12 Jun 2017 17:25:02 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kbuild test robot <fengguang.wu@...el.com>,
        Sean Young <sean@...s.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: [PATCH 4.11 095/150] [media] rc-core: race condition during ir_raw_event_register()

4.11-stable review patch.  If anyone has any objections, please let me know.

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

From: Sean Young <sean@...s.org>

commit 963761a0b2e85663ee4a5630f72930885a06598a upstream.

A rc device can call ir_raw_event_handle() after rc_allocate_device(),
but before rc_register_device() has completed. This is racey because
rcdev->raw is set before rcdev->raw->thread has a valid value.

Reported-by: kbuild test robot <fengguang.wu@...el.com>
Signed-off-by: Sean Young <sean@...s.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/media/rc/rc-ir-raw.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/media/rc/rc-ir-raw.c
+++ b/drivers/media/rc/rc-ir-raw.c
@@ -211,7 +211,7 @@ EXPORT_SYMBOL_GPL(ir_raw_event_set_idle)
  */
 void ir_raw_event_handle(struct rc_dev *dev)
 {
-	if (!dev->raw)
+	if (!dev->raw || !dev->raw->thread)
 		return;
 
 	wake_up_process(dev->raw->thread);
@@ -490,6 +490,7 @@ int ir_raw_event_register(struct rc_dev
 {
 	int rc;
 	struct ir_raw_handler *handler;
+	struct task_struct *thread;
 
 	if (!dev)
 		return -EINVAL;
@@ -507,13 +508,15 @@ int ir_raw_event_register(struct rc_dev
 	 * because the event is coming from userspace
 	 */
 	if (dev->driver_type != RC_DRIVER_IR_RAW_TX) {
-		dev->raw->thread = kthread_run(ir_raw_event_thread, dev->raw,
-					       "rc%u", dev->minor);
+		thread = kthread_run(ir_raw_event_thread, dev->raw, "rc%u",
+				     dev->minor);
 
-		if (IS_ERR(dev->raw->thread)) {
-			rc = PTR_ERR(dev->raw->thread);
+		if (IS_ERR(thread)) {
+			rc = PTR_ERR(thread);
 			goto out;
 		}
+
+		dev->raw->thread = thread;
 	}
 
 	mutex_lock(&ir_raw_handler_lock);