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
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