media: radio-raremono: change devm_k*alloc to k*alloc

Change devm_k*alloc to k*alloc to manually allocate memory

The manual allocation and freeing of memory is necessary because when
the USB radio is disconnected, the memory associated with devm_k*alloc
is freed. Meaning if we still have unresolved references to the radio
device, then we get use-after-free errors.

This patch fixes this by manually allocating memory, and freeing it in
the v4l2.release callback that gets called when the last radio device
exits.

Reported-and-tested-by: syzbot+a4387f5b6b799f6becbf@syzkaller.appspotmail.com
Signed-off-by: Luke Nowakowski-Krijger <lnowakow@eng.ucsd.edu>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: cleaned up two small checkpatch.pl warnings]
[hverkuil-cisco@xs4all.nl: prefix subject with driver name]
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/radio/radio-raremono.c

@@ -269,6 +269,14 @@ static int vidioc_g_frequency(struct file *file, void *priv,
 	return 0;
 }
 
+static void raremono_device_release(struct v4l2_device *v4l2_dev)
+{
+	struct raremono_device *radio = to_raremono_dev(v4l2_dev);
+
+	kfree(radio->buffer);
+	kfree(radio);
+}
+
 /* File system interface */
 static const struct v4l2_file_operations usb_raremono_fops = {
 	.owner		= THIS_MODULE,
@@ -293,12 +301,14 @@ static int usb_raremono_probe(struct usb_interface *intf,
 	struct raremono_device *radio;
 	int retval = 0;
 
-	radio = devm_kzalloc(&intf->dev, sizeof(struct raremono_device), GFP_KERNEL);
-	if (radio)
-		radio->buffer = devm_kmalloc(&intf->dev, BUFFER_LENGTH, GFP_KERNEL);
-
-	if (!radio || !radio->buffer)
+	radio = kzalloc(sizeof(*radio), GFP_KERNEL);
+	if (!radio)
+		return -ENOMEM;
+	radio->buffer = kmalloc(BUFFER_LENGTH, GFP_KERNEL);
+	if (!radio->buffer) {
+		kfree(radio);
 		return -ENOMEM;
+	}
 
 	radio->usbdev = interface_to_usbdev(intf);
 	radio->intf = intf;
@@ -322,7 +332,8 @@ static int usb_raremono_probe(struct usb_interface *intf,
 	if (retval != 3 ||
 	    (get_unaligned_be16(&radio->buffer[1]) & 0xfff) == 0x0242) {
 		dev_info(&intf->dev, "this is not Thanko's Raremono.\n");
-		return -ENODEV;
+		retval = -ENODEV;
+		goto free_mem;
 	}
 
 	dev_info(&intf->dev, "Thanko's Raremono connected: (%04X:%04X)\n",
@@ -331,7 +342,7 @@ static int usb_raremono_probe(struct usb_interface *intf,
 	retval = v4l2_device_register(&intf->dev, &radio->v4l2_dev);
 	if (retval < 0) {
 		dev_err(&intf->dev, "couldn't register v4l2_device\n");
-		return retval;
+		goto free_mem;
 	}
 
 	mutex_init(&radio->lock);
@@ -344,6 +355,7 @@ static int usb_raremono_probe(struct usb_interface *intf,
 	radio->vdev.lock = &radio->lock;
 	radio->vdev.release = video_device_release_empty;
 	radio->vdev.device_caps = V4L2_CAP_TUNER | V4L2_CAP_RADIO;
+	radio->v4l2_dev.release = raremono_device_release;
 
 	usb_set_intfdata(intf, &radio->v4l2_dev);
 
@@ -359,6 +371,10 @@ static int usb_raremono_probe(struct usb_interface *intf,
 	}
 	dev_err(&intf->dev, "could not register video device\n");
 	v4l2_device_unregister(&radio->v4l2_dev);
+
+free_mem:
+	kfree(radio->buffer);
+	kfree(radio);
 	return retval;
 }