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Subject: Re: [PATCH] ubi: block: fix null-pointer-dereference in
 ubiblock_create()
To: <linan666@huaweicloud.com>, <richard@nod.at>, <miquel.raynal@bootlin.com>,
	<vigneshr@ti.com>, <axboe@kernel.dk>, <chaitanya.kulkarni@wdc.com>
CC: <linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
	<yukuai3@huawei.com>, <yi.zhang@huawei.com>, <houtao1@huawei.com>,
	<yangerkun@huawei.com>
References: <20240428071922.2270892-1-linan666@huaweicloud.com>
From: Zhihao Cheng <chengzhihao1@huawei.com>
Message-ID: <98698009-e3a2-5c00-7619-6b6e3422cd1b@huawei.com>
Date: Sun, 28 Apr 2024 15:51:43 +0800
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?? 2024/4/28 15:19, linan666@huaweicloud.com д??:
> From: Li Nan <linan122@huawei.com>
> 
> Similar to commit adbf4c4954e3 ("ubi: block: fix memleak in
> ubiblock_create()"), 'dev->gd' is not assigned but dereferenced if
> blk_mq_alloc_tag_set() fails, and leading to a null-pointer-dereference.
> 
> Using 'gd' directly here is not a good idea, too. 'gd->part0.bd_device'
> is not initialized at this point. The error log will be:
>    block (null): block: dynamic minor allocation failed
> 
> Fix it by using pr_err() and print ubi id.
> 
> Fixes: 77567b25ab9f ("ubi: use blk_mq_alloc_disk and blk_cleanup_disk")
> Signed-off-by: Li Nan <linan122@huawei.com>
> ---
>   drivers/mtd/ubi/block.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
> index f82e3423acb9..bf7308e8ec2f 100644
> --- a/drivers/mtd/ubi/block.c
> +++ b/drivers/mtd/ubi/block.c
> @@ -390,7 +390,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
>   
>   	ret = blk_mq_alloc_tag_set(&dev->tag_set);
>   	if (ret) {
> -		dev_err(disk_to_dev(dev->gd), "blk_mq_alloc_tag_set failed");
> +		pr_err("ubiblock%d_%d: blk_mq_alloc_tag_set failed\n",
> +			dev->ubi_num, dev->vol_id);
>   		goto out_free_dev;
>   	}
>   
> @@ -407,8 +408,8 @@ int ubiblock_create(struct ubi_volume_info *vi)
>   	gd->minors = 1;
>   	gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, GFP_KERNEL);

There is no need to modify this place. The device of 'gd' is initialized 
in blk_mq_alloc_disk. Refer to nbd_dev_add.
>   	if (gd->first_minor < 0) {
> -		dev_err(disk_to_dev(gd),
> -			"block: dynamic minor allocation failed");
> +		pr_err("ubiblock%d_%d: block: dynamic minor allocation failed\n",
> +			dev->ubi_num, dev->vol_id);
>   		ret = -ENODEV;
>   		goto out_cleanup_disk;
>   	}
>