linux-kernel - Re: [PATCH] nullb: Adjust device size calculation in null_alloc

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Message-ID: <c0e09078-fa89-4dc7-9eab-415e19f22efe@linux.dev>
Date: Tue, 17 Sep 2024 15:21:02 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Aleksandr Mishin <amishin@...rgos.ru>, Shaohua Li <shli@...com>
Cc: Jens Axboe <axboe@...nel.dk>, Damien Le Moal <dlemoal@...nel.org>,
 Hannes Reinecke <hare@...e.de>,
 Johannes Thumshirn <johannes.thumshirn@....com>,
 Chaitanya Kulkarni <kch@...dia.com>,
 Chengming Zhou <zhouchengming@...edance.com>,
 John Garry <john.g.garry@...cle.com>, Yu Kuai <yukuai3@...wei.com>,
 Shin'ichiro Kawasaki <shinichiro.kawasaki@....com>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 lvc-project@...uxtesting.org
Subject: Re: [PATCH] nullb: Adjust device size calculation in null_alloc_dev()


在 2024/9/17 15:07, Aleksandr Mishin 写道:
> In null_alloc_dev() device size is a subject to overflow because 'g_gb'
> (which is module parameter, may have any value and is not validated
> anywhere) is not cast to a larger data type before performing arithmetic.
>
> Cast 'g_gb' to unsigned long to prevent overflow.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 2984c8684f96 ("nullb: factor disk parameters")
> Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
> ---
>   drivers/block/null_blk/main.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
> index 2f0431e42c49..5edbf9c0aceb 100644
> --- a/drivers/block/null_blk/main.c
> +++ b/drivers/block/null_blk/main.c
> @@ -762,7 +762,7 @@ static struct nullb_device *null_alloc_dev(void)
>   		return NULL;
>   	}
>   
> -	dev->size = g_gb * 1024;

The member variable size in struct nullb_device is type "unsigned long".

As such, changing g_gb from int to "unsigned long" seems reasonable.

So I am fine with this.

Reviewed-by: Zhu Yanjun <yanjun.zhu@...ux.dev>

Thanks a lot.

Zhu Yanjun

> +	dev->size = (unsigned long)g_gb * 1024;
>   	dev->completion_nsec = g_completion_nsec;
>   	dev->submit_queues = g_submit_queues;
>   	dev->prev_submit_queues = g_submit_queues;

-- 
Best Regards,
Yanjun.Zhu