media: v4l2-core: push taking ioctl mutex down to ioctl handler

The ioctl serialization mutex (vdev->lock or q->lock for vb2 queues)
was taken at the highest level in v4l2-dev.c. This prevents more
fine-grained locking since at that level we cannot examine the ioctl
arguments, we can only do that after video_usercopy is called.

So push the locking down to __video_do_ioctl() and subdev_do_ioctl_lock().

This also allows us to make a few functions in v4l2-ioctl.c static and
video_usercopy() is no longer exported.

The locking scheme is not changed by this patch, just pushed down.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 17 insertions, 3 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index c23fbfe90a9e..965fd301f617 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2655,14 +2655,15 @@ static struct v4l2_ioctl_info v4l2_ioctls[] = {
 };
 #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
 
-bool v4l2_is_known_ioctl(unsigned int cmd)
+static bool v4l2_is_known_ioctl(unsigned int cmd)
 {
 	if (_IOC_NR(cmd) >= V4L2_IOCTLS)
 		return false;
 	return v4l2_ioctls[_IOC_NR(cmd)].ioctl == cmd;
 }
 
-struct mutex *v4l2_ioctl_get_lock(struct video_device *vdev, unsigned cmd)
+static struct mutex *v4l2_ioctl_get_lock(struct video_device *vdev,
+					 unsigned int cmd)
 {
 	if (_IOC_NR(cmd) >= V4L2_IOCTLS)
 		return vdev->lock;
@@ -2713,6 +2714,7 @@ static long __video_do_ioctl(struct file *file,
 		unsigned int cmd, void *arg)
 {
 	struct video_device *vfd = video_devdata(file);
+	struct mutex *lock; /* ioctl serialization mutex */
 	const struct v4l2_ioctl_ops *ops = vfd->ioctl_ops;
 	bool write_only = false;
 	struct v4l2_ioctl_info default_info;
@@ -2731,6 +2733,16 @@ static long __video_do_ioctl(struct file *file,
 	if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags))
 		vfh = file->private_data;
 
+	lock = v4l2_ioctl_get_lock(vfd, cmd);
+
+	if (lock && mutex_lock_interruptible(lock))
+		return -ERESTARTSYS;
+
+	if (!video_is_registered(vfd)) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+
 	if (v4l2_is_known_ioctl(cmd)) {
 		info = &v4l2_ioctls[_IOC_NR(cmd)];
 
@@ -2780,6 +2792,9 @@ done:
 		}
 	}
 
+unlock:
+	if (lock)
+		mutex_unlock(lock);
 	return ret;
 }
 
@@ -2969,7 +2984,6 @@ out:
 	kvfree(mbuf);
 	return err;
 }
-EXPORT_SYMBOL(video_usercopy);
 
 long video_ioctl2(struct file *file,
 	       unsigned int cmd, unsigned long arg)