linux-kernel - Re: [net-next PATCH v4 1/3] sysctl: refactor integer handling proc code

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Message-ID: <4B7C178A.8010708@redhat.com>
Date:	Thu, 18 Feb 2010 00:21:30 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Octavian Purdila <opurdila@...acom.com>
CC:	David Miller <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Linux Kernel Developers <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [net-next PATCH v4 1/3] sysctl: refactor integer handling proc
 code

Octavian Purdila wrote:
> On Tuesday 16 February 2010 15:09:51 you wrote:
>> Octavian Purdila wrote:
>>> On Tuesday 16 February 2010 10:41:07 you wrote:
>>>>> +static int proc_skip_wspace(char __user **buf, size_t *size)
>>>>> +{
>>>>> +     char c;
>>>>> +
>>>>> +     while (*size) {
>>>>> +             if (get_user(c, *buf))
>>>>> +                     return -EFAULT;
>>>>> +             if (!isspace(c))
>>>>> +                     break;
>>>>> +             (*size)--; (*buf)++;
>>>>> +     }
>>>>> +
>>>>> +     return 0;
>>>>> +}
>>>> In lib/string.c we have skip_spaces(), I think we can use it
>>>> here instead of inventing another one.
>>> I'm afraid we can't, skip_spaces does not accept userspace buffers.
>> Well, you need to use copy_from_user() before call it.
>>
> 
> And how much would you copy? You need to either use a stack buffer and do a 
> loop copy or you would need to copy the whole userspace buffer which means we 
> need to allocate a kernel buffer. I think its much cleaner the way is currently 
> done.

Yeah, maybe just a personal preference. :-/

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