2019-11-30 09:37:53

by Wen Yang

Subject: [PATCH] UBI: fix use after free in ubi_remove_volume()

We can't use "vol" after it has been freed.

Fixes: 493cfaeaa0c9 ("mtd: utilize new cdev_device_add helper function")
Signed-off-by: Wen Yang <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Miquel Raynal <[email protected]>
Cc: Vignesh Raghavendra <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
drivers/mtd/ubi/vmt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 139ee13..8ff1478 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -375,7 +375,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
}

cdev_device_del(&vol->cdev, &vol->dev);
- put_device(&vol->dev);

spin_lock(&ubi->volumes_lock);
ubi->rsvd_pebs -= reserved_pebs;
@@ -388,6 +387,8 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
if (!no_vtbl)
self_check_volumes(ubi);

+ put_device(&vol->dev);
+
return 0;

out_err:
--
1.8.3.1

2019-12-03 13:14:43

by Hou Tao

Subject: Re: [PATCH] UBI: fix use after free in ubi_remove_volume()

Reviewed-by: Hou Tao <[email protected]>

On 2019/11/30 17:33, Wen Yang wrote:
> We can't use "vol" after it has been freed.
>
> Fixes: 493cfaeaa0c9 ("mtd: utilize new cdev_device_add helper function")
> Signed-off-by: Wen Yang <[email protected]>
> Cc: Richard Weinberger <[email protected]>
> Cc: Miquel Raynal <[email protected]>
> Cc: Vignesh Raghavendra <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> drivers/mtd/ubi/vmt.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> index 139ee13..8ff1478 100644
> --- a/drivers/mtd/ubi/vmt.c
> +++ b/drivers/mtd/ubi/vmt.c
> @@ -375,7 +375,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
> }
>
> cdev_device_del(&vol->cdev, &vol->dev);
> - put_device(&vol->dev);
>
> spin_lock(&ubi->volumes_lock);
> ubi->rsvd_pebs -= reserved_pebs;
> @@ -388,6 +387,8 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
> if (!no_vtbl)
> self_check_volumes(ubi);
>
> + put_device(&vol->dev);
> +
> return 0;
>
> out_err:
>

2019-12-05 01:34:09

by Hou Tao

Subject: Re: [PATCH] UBI: fix use after free in ubi_remove_volume()

Hi,

On 2019/12/3 21:13, Hou Tao wrote:
> Reviewed-by: Hou Tao <[email protected]>
>
Sorry for my early conclusion.

The reference of ubi_volume had already been increased in ubi_open_volume()
in ubi_cdev_ioctl(), so this reference dropped in ubi_remove_volume() will not
be the last one, and there will no use-after-free problem.

Regards,
Tao

> On 2019/11/30 17:33, Wen Yang wrote:
>> We can't use "vol" after it has been freed.
>>
>> Fixes: 493cfaeaa0c9 ("mtd: utilize new cdev_device_add helper function")
>> Signed-off-by: Wen Yang <[email protected]>
>> Cc: Richard Weinberger <[email protected]>
>> Cc: Miquel Raynal <[email protected]>
>> Cc: Vignesh Raghavendra <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> ---
>> drivers/mtd/ubi/vmt.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
>> index 139ee13..8ff1478 100644
>> --- a/drivers/mtd/ubi/vmt.c
>> +++ b/drivers/mtd/ubi/vmt.c
>> @@ -375,7 +375,6 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
>> }
>>
>> cdev_device_del(&vol->cdev, &vol->dev);
>> - put_device(&vol->dev);
>>
>> spin_lock(&ubi->volumes_lock);
>> ubi->rsvd_pebs -= reserved_pebs;
>> @@ -388,6 +387,8 @@ int ubi_remove_volume(struct ubi_volume_desc *desc, int no_vtbl)
>> if (!no_vtbl)
>> self_check_volumes(ubi);
>>
>> + put_device(&vol->dev);
>> +
>> return 0;
>>
>> out_err:
>>
>
>
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