[media] media: Refactor copying IOCTL arguments from and to user space

Refactor copying the IOCTL argument structs from the user space and back,
in order to reduce code copied around and make the implementation more
robust.

As a result, the copying is done while not holding the graph mutex.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/media-device.c

@@ -59,27 +59,24 @@ static int media_device_close(struct file *filp)
 }
 
 static int media_device_get_info(struct media_device *dev,
-				 struct media_device_info __user *__info)
+				 struct media_device_info *info)
 {
-	struct media_device_info info;
-
-	memset(&info, 0, sizeof(info));
+	memset(info, 0, sizeof(*info));
 
 	if (dev->driver_name[0])
-		strlcpy(info.driver, dev->driver_name, sizeof(info.driver));
+		strlcpy(info->driver, dev->driver_name, sizeof(info->driver));
 	else
-		strlcpy(info.driver, dev->dev->driver->name, sizeof(info.driver));
+		strlcpy(info->driver, dev->dev->driver->name,
+			sizeof(info->driver));
 
-	strlcpy(info.model, dev->model, sizeof(info.model));
-	strlcpy(info.serial, dev->serial, sizeof(info.serial));
-	strlcpy(info.bus_info, dev->bus_info, sizeof(info.bus_info));
+	strlcpy(info->model, dev->model, sizeof(info->model));
+	strlcpy(info->serial, dev->serial, sizeof(info->serial));
+	strlcpy(info->bus_info, dev->bus_info, sizeof(info->bus_info));
 
-	info.media_version = MEDIA_API_VERSION;
-	info.hw_revision = dev->hw_revision;
-	info.driver_version = dev->driver_version;
+	info->media_version = MEDIA_API_VERSION;
+	info->hw_revision = dev->hw_revision;
+	info->driver_version = dev->driver_version;
 
-	if (copy_to_user(__info, &info, sizeof(*__info)))
-		return -EFAULT;
 	return 0;
 }
 
@@ -101,29 +98,25 @@ static struct media_entity *find_entity(struct media_device *mdev, u32 id)
 }
 
 static long media_device_enum_entities(struct media_device *mdev,
-				       struct media_entity_desc __user *uent)
+				       struct media_entity_desc *entd)
 {
 	struct media_entity *ent;
-	struct media_entity_desc u_ent;
-
-	memset(&u_ent, 0, sizeof(u_ent));
-	if (copy_from_user(&u_ent.id, &uent->id, sizeof(u_ent.id)))
-		return -EFAULT;
-
-	ent = find_entity(mdev, u_ent.id);
 
+	ent = find_entity(mdev, entd->id);
 	if (ent == NULL)
 		return -EINVAL;
 
-	u_ent.id = media_entity_id(ent);
+	memset(entd, 0, sizeof(*entd));
+
+	entd->id = media_entity_id(ent);
 	if (ent->name)
-		strlcpy(u_ent.name, ent->name, sizeof(u_ent.name));
-	u_ent.type = ent->function;
-	u_ent.revision = 0;		/* Unused */
-	u_ent.flags = ent->flags;
-	u_ent.group_id = 0;		/* Unused */
-	u_ent.pads = ent->num_pads;
-	u_ent.links = ent->num_links - ent->num_backlinks;
+		strlcpy(entd->name, ent->name, sizeof(entd->name));
+	entd->type = ent->function;
+	entd->revision = 0;		/* Unused */
+	entd->flags = ent->flags;
+	entd->group_id = 0;		/* Unused */
+	entd->pads = ent->num_pads;
+	entd->links = ent->num_links - ent->num_backlinks;
 
 	/*
 	 * Workaround for a bug at media-ctl <= v1.10 that makes it to
@@ -139,14 +132,13 @@ static long media_device_enum_entities(struct media_device *mdev,
 	if (ent->function < MEDIA_ENT_F_OLD_BASE ||
 	    ent->function > MEDIA_ENT_T_DEVNODE_UNKNOWN) {
 		if (is_media_entity_v4l2_subdev(ent))
-			u_ent.type = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
+			entd->type = MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN;
 		else if (ent->function != MEDIA_ENT_F_IO_V4L)
-			u_ent.type = MEDIA_ENT_T_DEVNODE_UNKNOWN;
+			entd->type = MEDIA_ENT_T_DEVNODE_UNKNOWN;
 	}
 
-	memcpy(&u_ent.raw, &ent->info, sizeof(ent->info));
-	if (copy_to_user(uent, &u_ent, sizeof(u_ent)))
-		return -EFAULT;
+	memcpy(&entd->raw, &ent->info, sizeof(ent->info));
+
 	return 0;
 }
 
@@ -158,7 +150,7 @@ static void media_device_kpad_to_upad(const struct media_pad *kpad,
 	upad->flags = kpad->flags;
 }
 
-static long __media_device_enum_links(struct media_device *mdev,
+static long media_device_enum_links(struct media_device *mdev,
 				    struct media_links_enum *links)
 {
 	struct media_entity *entity;
@@ -206,64 +198,35 @@ static long __media_device_enum_links(struct media_device *mdev,
 	return 0;
 }
 
-static long media_device_enum_links(struct media_device *mdev,
-				    struct media_links_enum __user *ulinks)
-{
-	struct media_links_enum links;
-	int rval;
-
-	if (copy_from_user(&links, ulinks, sizeof(links)))
-		return -EFAULT;
-
-	rval = __media_device_enum_links(mdev, &links);
-	if (rval < 0)
-		return rval;
-
-	if (copy_to_user(ulinks, &links, sizeof(*ulinks)))
-		return -EFAULT;
-
-	return 0;
-}
-
 static long media_device_setup_link(struct media_device *mdev,
-				    struct media_link_desc __user *_ulink)
+				    struct media_link_desc *linkd)
 {
 	struct media_link *link = NULL;
-	struct media_link_desc ulink;
 	struct media_entity *source;
 	struct media_entity *sink;
-	int ret;
-
-	if (copy_from_user(&ulink, _ulink, sizeof(ulink)))
-		return -EFAULT;
 
 	/* Find the source and sink entities and link.
 	 */
-	source = find_entity(mdev, ulink.source.entity);
-	sink = find_entity(mdev, ulink.sink.entity);
+	source = find_entity(mdev, linkd->source.entity);
+	sink = find_entity(mdev, linkd->sink.entity);
 
 	if (source == NULL || sink == NULL)
 		return -EINVAL;
 
-	if (ulink.source.index >= source->num_pads ||
-	    ulink.sink.index >= sink->num_pads)
+	if (linkd->source.index >= source->num_pads ||
+	    linkd->sink.index >= sink->num_pads)
 		return -EINVAL;
 
-	link = media_entity_find_link(&source->pads[ulink.source.index],
-				      &sink->pads[ulink.sink.index]);
+	link = media_entity_find_link(&source->pads[linkd->source.index],
+				      &sink->pads[linkd->sink.index]);
 	if (link == NULL)
 		return -EINVAL;
 
 	/* Setup the link on both entities. */
-	ret = __media_entity_setup_link(link, ulink.flags);
-
-	if (copy_to_user(_ulink, &ulink, sizeof(ulink)))
-		return -EFAULT;
-
-	return ret;
+	return __media_entity_setup_link(link, linkd->flags);
 }
 
-static long __media_device_get_topology(struct media_device *mdev,
+static long media_device_get_topology(struct media_device *mdev,
 				      struct media_v2_topology *topo)
 {
 	struct media_entity *entity;
@@ -400,35 +363,41 @@ static long __media_device_get_topology(struct media_device *mdev,
 	return ret;
 }
 
-static long media_device_get_topology(struct media_device *mdev,
-				      struct media_v2_topology __user *utopo)
+static long copy_arg_from_user(void *karg, void __user *uarg, unsigned int cmd)
 {
-	struct media_v2_topology ktopo;
-	int ret;
-
-	if (copy_from_user(&ktopo, utopo, sizeof(ktopo)))
+	/* All media IOCTLs are _IOWR() */
+	if (copy_from_user(karg, uarg, _IOC_SIZE(cmd)))
 		return -EFAULT;
 
-	ret = __media_device_get_topology(mdev, &ktopo);
-	if (ret < 0)
-		return ret;
+	return 0;
+}
 
-	if (copy_to_user(utopo, &ktopo, sizeof(*utopo)))
+static long copy_arg_to_user(void __user *uarg, void *karg, unsigned int cmd)
+{
+	/* All media IOCTLs are _IOWR() */
+	if (copy_to_user(uarg, karg, _IOC_SIZE(cmd)))
 		return -EFAULT;
 
 	return 0;
 }
 
-#define MEDIA_IOC(__cmd, func)						\
+#define MEDIA_IOC_ARG(__cmd, func, from_user, to_user)	\
 	[_IOC_NR(MEDIA_IOC_##__cmd)] = {		\
 		.cmd = MEDIA_IOC_##__cmd,		\
-		.fn = (long (*)(struct media_device *, void __user *))func,    \
+		.fn = (long (*)(struct media_device *, void *))func,	\
+		.arg_from_user = from_user,		\
+		.arg_to_user = to_user,			\
 	}
 
+#define MEDIA_IOC(__cmd, func)						\
+	MEDIA_IOC_ARG(__cmd, func, copy_arg_from_user, copy_arg_to_user)
+
 /* the table is indexed by _IOC_NR(cmd) */
 struct media_ioctl_info {
 	unsigned int cmd;
-	long (*fn)(struct media_device *dev, void __user *arg);
+	long (*fn)(struct media_device *dev, void *arg);
+	long (*arg_from_user)(void *karg, void __user *uarg, unsigned int cmd);
+	long (*arg_to_user)(void __user *uarg, void *karg, unsigned int cmd);
 };
 
 static const struct media_ioctl_info ioctl_info[] = {
@@ -440,11 +409,13 @@ static const struct media_ioctl_info ioctl_info[] = {
 };
 
 static long media_device_ioctl(struct file *filp, unsigned int cmd,
-			       unsigned long arg)
+			       unsigned long __arg)
 {
 	struct media_devnode *devnode = media_devnode_data(filp);
 	struct media_device *dev = devnode->media_dev;
 	const struct media_ioctl_info *info;
+	void __user *arg = (void __user *)__arg;
+	char __karg[256], *karg = __karg;
 	long ret;
 
 	if (_IOC_NR(cmd) >= ARRAY_SIZE(ioctl_info)
@@ -453,10 +424,29 @@ static long media_device_ioctl(struct file *filp, unsigned int cmd,
 
 	info = &ioctl_info[_IOC_NR(cmd)];
 
+	if (_IOC_SIZE(info->cmd) > sizeof(__karg)) {
+		karg = kmalloc(_IOC_SIZE(info->cmd), GFP_KERNEL);
+		if (!karg)
+			return -ENOMEM;
+	}
+
+	if (info->arg_from_user) {
+		ret = info->arg_from_user(karg, arg, cmd);
+		if (ret)
+			goto out_free;
+	}
+
 	mutex_lock(&dev->graph_mutex);
-	ret = info->fn(dev, (void __user *)arg);
+	ret = info->fn(dev, karg);
 	mutex_unlock(&dev->graph_mutex);
 
+	if (!ret && info->arg_to_user)
+		ret = info->arg_to_user(arg, karg, cmd);
+
+out_free:
+	if (karg != __karg)
+		kfree(karg);
+
 	return ret;
 }
 
@@ -485,7 +475,7 @@ static long media_device_enum_links32(struct media_device *mdev,
 	links.pads = compat_ptr(pads_ptr);
 	links.links = compat_ptr(links_ptr);
 
-	return __media_device_enum_links(mdev, &links);
+	return media_device_enum_links(mdev, &links);
 }
 
 #define MEDIA_IOC_ENUM_LINKS32		_IOWR('|', 0x02, struct media_links_enum32)