Re: [Patch 1/3] sysctl: refactor integer handling proc code

[Cong Wang]

Alexey Dobriyan wrote:
> On Mon, Apr 12, 2010 at 06:04:04AM -0400, Amerigo Wang wrote:
> > As we are about to add another integer handling proc function a little
> > bit of cleanup is in order: add a few helper functions to improve code
> > readability and decrease code duplication.
> >
> > In the process a bug is also fixed: if the user specifies a number
> > with more then 20 digits it will be interpreted as two integers
> > (e.g. 10000...13 will be interpreted as 100.... and 13).
>
> ULONG_MAX is not 22 digits always.
>
> The fix is to not rely on simple_strtoul()
>
> I guess it's time to finally remove it. :-(


Or use strict_strtoul()?

> Also, it's better to copy_from user stuff once.
> Without looking at non-trivial users, one page should be enough.

It seems that all proc code assumes that the input buffer will
not exceed one page size.


> > Behavior for EFAULT handling was changed as well. Previous to this
> > patch, when an EFAULT error occurred in the middle of a write
> > operation, although some of the elements were set, that was not
> > acknowledged to the user (by shorting the write and returning the
> > number of bytes accepted). EFAULT is now treated just like any other
> > errors by acknowledging the amount of bytes accepted.
>
> > +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;
> > +}
>
> yeah, copy_from_user once, so we won't have this.

Ok.

> > +static bool isanyof(char c, const char *v, unsigned len)
>
> A what?
> this is memchr()

Hmm, right, it should be memchr(v, c, len).

Thanks!

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