linux-kernel - Re: [PATCH] ubi: block: fix null-pointer-dereference in ubiblock

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Date:   Fri, 8 Dec 2023 15:29:35 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <linan666@...weicloud.com>, <richard@....at>,
        <miquel.raynal@...tlin.com>, <vigneshr@...com>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linan122@...wei.com>, <yukuai3@...wei.com>, <yi.zhang@...wei.com>,
        <houtao1@...wei.com>, <yangerkun@...wei.com>
Subject: Re: [PATCH] ubi: block: fix null-pointer-dereference in
 ubiblock_create()

在 2023/12/8 15:13, linan666@...weicloud.com 写道:
> From: Li Nan <linan122@...wei.com>
>
> If idr_alloc() fails, dev->gd will be put after goto out_cleanup_disk in
> ubiblock_create(), but dev->gd has not been assigned yet at this time, and
> accessing it will trigger a null-pointer-dereference issue. Fix it by put
> gd directly.
Function 'put_disk()' checks disk whether is NULL, so I think it's a 
'memleak' problem, not a null-ptr-deref problem.
>
> Signed-off-by: Li Nan <linan122@...wei.com>
> ---
>   drivers/mtd/ubi/block.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
> index 309a42aeaa4c..654bd7372cd8 100644
> --- a/drivers/mtd/ubi/block.c
> +++ b/drivers/mtd/ubi/block.c
> @@ -434,7 +434,7 @@ int ubiblock_create(struct ubi_volume_info *vi)
>   	list_del(&dev->list);
>   	idr_remove(&ubiblock_minor_idr, gd->first_minor);
>   out_cleanup_disk:
> -	put_disk(dev->gd);
> +	put_disk(gd);

For memleak solution:

Reviewed-by: Zhihao Cheng <chengzhihao1@...wei.com>

>   out_free_tags:
>   	blk_mq_free_tag_set(&dev->tag_set);
>   out_free_dev: