linux-kernel - Re: [PATCH -next] nbd: fix possible overflow on 'first_minor' in nbd_dev

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Message-ID: <4f9e579e-1604-4bd4-f988-cb038e3ebdc3@huawei.com>
Date:   Thu, 31 Mar 2022 08:45:27 +0800
From:   "zhangwensheng (E)" <zhangwensheng5@...wei.com>
To:     <josef@...icpanda.com>, <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <nbd@...er.debian.org>, <yukuai3@...wei.com>
Subject: Re: [PATCH -next] nbd: fix possible overflow on 'first_minor' in
 nbd_dev_add()

friendly ping...

在 2022/3/17 21:05, zhangwensheng (E) 写道:
> friendly ping...
>
> 在 2022/3/11 10:43, zhangwensheng (E) 写道:
>> friendly ping...
>>
>> 在 2022/3/10 17:32, Zhang Wensheng 写道:
>>> When 'index' is a big numbers, it may become negative which forced
>>> to 'int'. then 'index << part_shift' might overflow to a positive
>>> value that is not greater than '0xfffff', then sysfs might complains
>>> about duplicate creation. Because of this, move the 'index' judgment
>>> to the front will fix it and be better.
>>>
>>> Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices")
>>> Fixes: 940c264984fd ("nbd: fix possible overflow for 'first_minor' 
>>> in nbd_dev_add()")
>>> Signed-off-by: Zhang Wensheng <zhangwensheng5@...wei.com>
>>> ---
>>>   drivers/block/nbd.c | 24 ++++++++++++------------
>>>   1 file changed, 12 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
>>> index 5a1f98494ddd..b3cdfc0ffb98 100644
>>> --- a/drivers/block/nbd.c
>>> +++ b/drivers/block/nbd.c
>>> @@ -1800,17 +1800,6 @@ static struct nbd_device *nbd_dev_add(int 
>>> index, unsigned int refs)
>>>       refcount_set(&nbd->refs, 0);
>>>       INIT_LIST_HEAD(&nbd->list);
>>>       disk->major = NBD_MAJOR;
>>> -
>>> -    /* Too big first_minor can cause duplicate creation of
>>> -     * sysfs files/links, since index << part_shift might overflow, or
>>> -     * MKDEV() expect that the max bits of first_minor is 20.
>>> -     */
>>> -    disk->first_minor = index << part_shift;
>>> -    if (disk->first_minor < index || disk->first_minor > MINORMASK) {
>>> -        err = -EINVAL;
>>> -        goto out_free_work;
>>> -    }
>>> -
>>>       disk->minors = 1 << part_shift;
>>>       disk->fops = &nbd_fops;
>>>       disk->private_data = nbd;
>>> @@ -1915,8 +1904,19 @@ static int nbd_genl_connect(struct sk_buff 
>>> *skb, struct genl_info *info)
>>>       if (!netlink_capable(skb, CAP_SYS_ADMIN))
>>>           return -EPERM;
>>>   -    if (info->attrs[NBD_ATTR_INDEX])
>>> +    if (info->attrs[NBD_ATTR_INDEX]) {
>>>           index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
>>> +
>>> +        /*
>>> +         * Too big first_minor can cause duplicate creation of
>>> +         * sysfs files/links, since index << part_shift might 
>>> overflow, or
>>> +         * MKDEV() expect that the max bits of first_minor is 20.
>>> +         */
>>> +        if (index < 0 || index > MINORMASK >> part_shift) {
>>> +            printk(KERN_ERR "nbd: illegal input index %d\n", index);
>>> +            return -EINVAL;
>>> +        }
>>> +    }
>>>       if (!info->attrs[NBD_ATTR_SOCKETS]) {
>>>           printk(KERN_ERR "nbd: must specify at least one socket\n");
>>>           return -EINVAL;
>> .
> .