linux-kernel - Re: [PATCH] UBI: fix use after free in ubi_remove

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Message-ID: <65b49705-e28c-e077-c0de-c5167e34d1c5@huawei.com>
Date:   Tue, 3 Dec 2019 21:13:01 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     Wen Yang <wenyang@...ux.alibaba.com>,
        Richard Weinberger <richard@....at>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>
CC:     <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <xlpang@...ux.alibaba.com>
Subject: Re: [PATCH] UBI: fix use after free in ubi_remove_volume()

Reviewed-by: Hou Tao <houtao1@...wei.com>

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 <wenyang@...ux.alibaba.com>
> Cc: Richard Weinberger <richard@....at>
> Cc: Miquel Raynal <miquel.raynal@...tlin.com>
> Cc: Vignesh Raghavendra <vigneshr@...com>
> Cc: linux-mtd@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  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:
>