Patch "media: rc: uevent sysfs file races with rc_unregister_device()" has been added to the 4.19-stable tree

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This is a note to let you know that I've just added the patch titled

    media: rc: uevent sysfs file races with rc_unregister_device()

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     media-rc-uevent-sysfs-file-races-with-rc_unregister_device.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 4f0835d6677dc69263f90f976524cb92b257d9f4 Mon Sep 17 00:00:00 2001
From: Sean Young <sean@xxxxxxxx>
Date: Sat, 8 Aug 2020 13:19:12 +0200
Subject: media: rc: uevent sysfs file races with rc_unregister_device()

From: Sean Young <sean@xxxxxxxx>

commit 4f0835d6677dc69263f90f976524cb92b257d9f4 upstream.

Only report uevent file contents if device still registered, else we
might read freed memory.

Reported-by: syzbot+ceef16277388d6f24898@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.16+
Signed-off-by: Sean Young <sean@xxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/media/rc/rc-main.c |   32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

--- a/drivers/media/rc/rc-main.c
+++ b/drivers/media/rc/rc-main.c
@@ -1568,25 +1568,25 @@ static void rc_dev_release(struct device
 	kfree(dev);
 }
 
-#define ADD_HOTPLUG_VAR(fmt, val...)					\
-	do {								\
-		int err = add_uevent_var(env, fmt, val);		\
-		if (err)						\
-			return err;					\
-	} while (0)
-
 static int rc_dev_uevent(struct device *device, struct kobj_uevent_env *env)
 {
 	struct rc_dev *dev = to_rc_dev(device);
+	int ret = 0;
 
-	if (dev->rc_map.name)
-		ADD_HOTPLUG_VAR("NAME=%s", dev->rc_map.name);
-	if (dev->driver_name)
-		ADD_HOTPLUG_VAR("DRV_NAME=%s", dev->driver_name);
-	if (dev->device_name)
-		ADD_HOTPLUG_VAR("DEV_NAME=%s", dev->device_name);
+	mutex_lock(&dev->lock);
 
-	return 0;
+	if (!dev->registered)
+		ret = -ENODEV;
+	if (ret == 0 && dev->rc_map.name)
+		ret = add_uevent_var(env, "NAME=%s", dev->rc_map.name);
+	if (ret == 0 && dev->driver_name)
+		ret = add_uevent_var(env, "DRV_NAME=%s", dev->driver_name);
+	if (ret == 0 && dev->device_name)
+		ret = add_uevent_var(env, "DEV_NAME=%s", dev->device_name);
+
+	mutex_unlock(&dev->lock);
+
+	return ret;
 }
 
 /*
@@ -1970,14 +1970,14 @@ void rc_unregister_device(struct rc_dev
 	del_timer_sync(&dev->timer_keyup);
 	del_timer_sync(&dev->timer_repeat);
 
-	rc_free_rx_device(dev);
-
 	mutex_lock(&dev->lock);
 	if (dev->users && dev->close)
 		dev->close(dev);
 	dev->registered = false;
 	mutex_unlock(&dev->lock);
 
+	rc_free_rx_device(dev);
+
 	/*
 	 * lirc device should be freed with dev->registered = false, so
 	 * that userspace polling will get notified.


Patches currently in stable-queue which might be from sean@xxxxxxxx are

queue-4.19/media-rc-do-not-access-device-via-sysfs-after-rc_unregister_device.patch
queue-4.19/media-rc-uevent-sysfs-file-races-with-rc_unregister_device.patch



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