Re: [PATCH v4 3/5] media: Refactor copying IOCTL arguments from and to user space

Laurent Pinchart
2016-09-02T15:31:12Z

Hi Sakari,

Thank you for the patch.

On Thursday 11 Aug 2016 23:29:16 Sakari Ailus wrote:
> 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>

> ---
> drivers/media/media-device.c | 190 +++++++++++++++++----------------------
> 1 file changed, 90 insertions(+), 100 deletions(-)
>
> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> index cc6c566..d1b47a4 100644
> --- a/drivers/media/media-device.c
> +++ b/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;
> }
>
> @@ -158,8 +150,8 @@ 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,
> - struct media_links_enum *links)
> +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)
\
> - [_IOC_NR(MEDIA_IOC_##__cmd)] = { \
> - .cmd = MEDIA_IOC_##__cmd, \
> - .fn = (long (*)(struct media_device *, void __user *))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 *))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[] = {
> @@ -453,6 +422,7 @@ static long __media_device_ioctl(
> struct media_devnode *devnode = media_devnode_data(filp);
> struct media_device *dev = devnode->media_dev;
> const struct media_ioctl_info *info;
> + char __karg[256], *karg = __karg;
> long ret;
>
> ret = is_valid_ioctl(info_array, cmd);
> @@ -461,10 +431,29 @@ static long __media_device_ioctl(
>
> info = &info_array[_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, 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;
> }
>
> @@ -484,23 +473,24 @@ struct media_links_enum32 {
> __u32 reserved[4];
> };
>
> -static long media_device_enum_links32(struct media_device *mdev,
> - struct media_links_enum32 __user
*ulinks)
> +static long from_user_enum_links32(void *karg, void __user *uarg,
> + unsigned int cmd)
> {
> - struct media_links_enum links;
> + struct media_links_enum *links = karg;
> + struct media_links_enum32 __user *ulinks = uarg;
> compat_uptr_t pads_ptr, links_ptr;
>
> - memset(&links, 0, sizeof(links));
> + memset(links, 0, sizeof(*links));
>
> - if (get_user(links.entity, &ulinks->entity)
> + if (get_user(links->entity, &ulinks->entity)
> || get_user(pads_ptr, &ulinks->pads)
> || get_user(links_ptr, &ulinks->links))
> return -EFAULT;
>
> - links.pads = compat_ptr(pads_ptr);
> - links.links = compat_ptr(links_ptr);
> + links->pads = compat_ptr(pads_ptr);
> + links->links = compat_ptr(links_ptr);
>
> - return __media_device_enum_links(mdev, &links);
> + return 0;
> }
>
> #define MEDIA_IOC_ENUM_LINKS32 _IOWR('|', 0x02, struct
media_links_enum32)
> @@ -508,7 +498,7 @@ static long media_device_enum_links32(struct
> media_device *mdev, static const struct media_ioctl_info
> compat_ioctl_info[] = {
> MEDIA_IOC(DEVICE_INFO, media_device_get_info),
> MEDIA_IOC(ENUM_ENTITIES, media_device_enum_entities),
> - MEDIA_IOC(ENUM_LINKS32, media_device_enum_links32),
> + MEDIA_IOC_ARG(ENUM_LINKS32, media_device_enum_links,
> from_user_enum_links32, NULL),
> MEDIA_IOC(SETUP_LINK, media_device_setup_link),
> MEDIA_IOC(G_TOPOLOGY, media_device_get_topology),
> };

--
Regards,

Laurent Pinchart