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

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

[Yang Yingliang]

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.

Fix this by adding some checks.

Fixes: 801c135ce73d ("UBI: Unsorted Block Images")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/mtd/ubi/vmt.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 8fcc0bdf0635..c379b8739f52 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -614,8 +614,14 @@ void ubi_free_volume(struct ubi_device *ubi, struct ubi_volume *vol)
 	dbg_gen("free volume %d", vol->vol_id);
 
 	ubi->volumes[vol->vol_id] = NULL;
-	cdev_del(&vol->cdev);
-	device_unregister(&vol->dev);
+	if (device_is_registered(&vol->dev)) {
+		cdev_del(&vol->cdev);
+		device_unregister(&vol->dev);
+	} else if (vol->dev.kobj.state_initialized) {
+		put_device(&vol->dev);
+	} else {
+		kfree(vol);
+	}
 }
 
 /**
-- 
2.25.1


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

[Zhihao Cheng]

在 2022/11/11 22:48, Yang Yingliang 写道:

[...]
> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> index 8fcc0bdf0635..c379b8739f52 100644
> --- a/drivers/mtd/ubi/vmt.c
> +++ b/drivers/mtd/ubi/vmt.c
> @@ -614,8 +614,14 @@ void ubi_free_volume(struct ubi_device *ubi, struct ubi_volume *vol)
>   	dbg_gen("free volume %d", vol->vol_id);
>   
>   	ubi->volumes[vol->vol_id] = NULL;
> -	cdev_del(&vol->cdev);
> -	device_unregister(&vol->dev);
> +	if (device_is_registered(&vol->dev)) {
> +		cdev_del(&vol->cdev);
> +		device_unregister(&vol->dev);
> +	} else if (vol->dev.kobj.state_initialized) {
> +		put_device(&vol->dev);
> +	} else {

Following process will trigger a memleak after this patch applied.

ubi_attach
  ubi_read_volume_table
   init_volumes
    ubi_fastmap_init_checkmap
     vol->checkmap = bitmap_zalloc(leb_count, GFP_KERNEL);    // alloc 
bitmap
  ubi_eba_init
   ubi_eba_replace_table
    vol->eba_tbl = tbl                            // alloc eba_tbl

uif_init
  ubi_add_volume
   cdev_add   // failed
  kill_volumes
   ubi_free_volume
    kfree(vol)                     // miss freeing eba_tbl and bitmap
> +		kfree(vol);
> +	}
>   }
>   
>   /**
> 


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