netdev - Re: [PATCH net-next 1/8] atm: use min() to simplify the code

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Message-ID: <01f3dd36-e4b6-4769-ba10-cdd0856a1076@huawei.com>
Date: Thu, 22 Aug 2024 21:50:34 +0800
From: Li Zetao <lizetao1@...wei.com>
To: "Dr. David Alan Gilbert" <linux@...blig.org>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <marcel@...tmann.org>, <johan.hedberg@...il.com>,
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	<netdev@...r.kernel.org>, <linux-bluetooth@...r.kernel.org>,
	<ceph-devel@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
	<tipc-discussion@...ts.sourceforge.net>
Subject: Re: [PATCH net-next 1/8] atm: use min() to simplify the code

Hi,

在 2024/8/22 21:39, Dr. David Alan Gilbert 写道:
> * Li Zetao (lizetao1@...wei.com) wrote:
>> When copying data to user, it needs to determine the copy length.
>> It is easier to understand using min() here.
>>
>> Signed-off-by: Li Zetao <lizetao1@...wei.com>
>> ---
>>   net/atm/addr.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/atm/addr.c b/net/atm/addr.c
>> index 0530b63f509a..6c4c942b2cb9 100644
>> --- a/net/atm/addr.c
>> +++ b/net/atm/addr.c
>> @@ -136,7 +136,7 @@ int atm_get_addr(struct atm_dev *dev, struct sockaddr_atmsvc __user * buf,
>>   	unsigned long flags;
>>   	struct atm_dev_addr *this;
>>   	struct list_head *head;
>> -	int total = 0, error;
>> +	size_t total = 0, error;
> 
> Aren't you accidentally changing the type of 'error' there, and the function
> returns 'int'.
This is intentionally modified because the input parameter size is of 
type size_t. If total is of type int, the compiler will report an error 
when the min() is called.
> 
> Dav
> 
> 
>>   	struct sockaddr_atmsvc *tmp_buf, *tmp_bufp;
>>   
>>   	spin_lock_irqsave(&dev->lock, flags);
>> @@ -155,7 +155,7 @@ int atm_get_addr(struct atm_dev *dev, struct sockaddr_atmsvc __user * buf,
>>   	    memcpy(tmp_bufp++, &this->addr, sizeof(struct sockaddr_atmsvc));
>>   	spin_unlock_irqrestore(&dev->lock, flags);
>>   	error = total > size ? -E2BIG : total;
>> -	if (copy_to_user(buf, tmp_buf, total < size ? total : size))
>> +	if (copy_to_user(buf, tmp_buf, min(total, size)))
>>   		error = -EFAULT;
>>   	kfree(tmp_buf);
>>   	return error;
>> -- 
>> 2.34.1
>>

Thanks,
Li Zetao.