[PATCH v3] mtd: ubi: fix possible null-ptr-deref in ubi_free_volume()

[Zhihao Cheng]

在 2022/11/14 18:26, Yang Yingliang 写道:

Reviewed-by: Zhihao Cheng <chengzhihao1 at huawei.com>

> It willl cause null-ptr-deref in the following case:
> 
> uif_init()
>    ubi_add_volume()
>      cdev_add() -> if it fails, call kill_volumes()
>      device_register()
> 
> kill_volumes() -> if ubi_add_volume() fails call this function
>    ubi_free_volume()
>      cdev_del()
>      device_unregister() -> trying to delete a not added device,
> 			   it causes null-ptr-deref
> 
> So in ubi_free_volume(), it delete devices whether they are added
> or not, it will causes null-ptr-deref.
> 
> Handle the error case whlie calling ubi_add_volume() to fix this
> problem. If add volume fails, set the corresponding vol to null,
> so it can not be accessed in kill_volumes() and release the
> resource in ubi_add_volume() error path.
> 
> Fixes: 801c135ce73d ("UBI: Unsorted Block Images")
> Suggested-by: Zhihao Cheng <chengzhihao1 at huawei.com>
> Signed-off-by: Yang Yingliang <yangyingliang at huawei.com>
> ---
> v2 -> v3:
>    Handle the error case whlie calling ubi_add_volume().
> 
> v1 -> v2:
>    Replace kfree() with vol_release() to avoid memory leak, if device is not initalized.
> ---
>   drivers/mtd/ubi/build.c |  1 +
>   drivers/mtd/ubi/vmt.c   | 12 ++++++------
>   2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
> index a901f8edfa41..4990c99eeb56 100644
> --- a/drivers/mtd/ubi/build.c
> +++ b/drivers/mtd/ubi/build.c
> @@ -468,6 +468,7 @@ static int uif_init(struct ubi_device *ubi)
>   			err = ubi_add_volume(ubi, ubi->volumes[i]);
>   			if (err) {
>   				ubi_err(ubi, "cannot add volume %d", i);
> +				ubi->volumes[i] = NULL;
>   				goto out_volumes;
>   			}
>   		}
> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> index 8fcc0bdf0635..c663ad14c503 100644
> --- a/drivers/mtd/ubi/vmt.c
> +++ b/drivers/mtd/ubi/vmt.c
> @@ -580,6 +580,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
>   	if (err) {
>   		ubi_err(ubi, "cannot add character device for volume %d, error %d",
>   			vol_id, err);
> +		vol_release(&vol->dev);
>   		return err;
>   	}
>   
> @@ -590,15 +591,14 @@ int ubi_add_volume(struct ubi_device *ubi, struct ubi_volume *vol)
>   	vol->dev.groups = volume_dev_groups;
>   	dev_set_name(&vol->dev, "%s_%d", ubi->ubi_name, vol->vol_id);
>   	err = device_register(&vol->dev);
> -	if (err)
> -		goto out_cdev;
> +	if (err) {
> +		cdev_del(&vol->cdev);
> +		put_device(&vol->dev);
> +		return err;
> +	}
>   
>   	self_check_volumes(ubi);
>   	return err;
> -
> -out_cdev:
> -	cdev_del(&vol->cdev);
> -	return err;
>   }
>   
>   /**
>