Re: [RFC][CFLART] ipmi procfs bogosity

[Corey Minyard <minyard@acm.org>]

viro@ZenIV.linux.org.uk wrote:

>On Thu, Sep 01, 2005 at 11:41:42AM -0500, Corey Minyard wrote:
>  
>
>>Indeed, this function is badly written.  In rewriting, I couldn't find a
>>nice function for reading integers from userspace, and the proc_dointvec
>>stuff didn't seem terribly suitable.  So I wrote my own general
>>function, which I can move someplace else if someone likes.  Patch is
>>attached.  It should not affect correct usage of this file.
>>    
>>
>
>Eeeek...  Much, _much_ simpler approach would be to have
>
>	char buf[10];
>	if (count > 9)
>		return -EINVAL;
>	if (copy_from_user(buf, buffer, count))
>		return -EFAULT;
>	buf[count] = '\0';
>	/* use sscanf() or anything normal */
>
>Would that change behaviour in any cases you care about?
>  
>
Because then, for a general solution that avoids integer
perversion, you need something like:

    char         buf[10];
    char         *end;

    if (count > (sizeof(buf) - 1))
        return -EINVAL;
    if (copy_from_user(buf, buffer, count))
        return -EFAULT;
    buf[count] = '\0';
    newval = simple_strtoul(buf, &end, 0);
    if (buf == end)
        /* Empty string or first char not a number */
        return -EINVAL;
    if (*end && ! isspace(*end))
        /* Bogus number. */
        return -EINVAL;


To me, It's a lot nicer to do:

    rv = user_strtoul(....);
    if (rv < 0)
        return rv;

Plus the scanning function I wrote handles arbitrary leading and 
trailing space, etc.  Not a big deal, but a little nicer.

-Corey