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SubjectRe: [PATCH 1/6] property: add fwnode_property_read_string_index()
On Mon, Mar 21, 2022 at 08:49:21AM +0100, Clément Léger wrote:
> Le Fri, 18 Mar 2022 20:09:37 +0200,
> Andy Shevchenko <andriy.shevchenko@linux.intel.com> a écrit :
> > On Fri, Mar 18, 2022 at 05:49:12PM +0100, Clément Léger wrote:
> > > Le Fri, 18 Mar 2022 18:26:00 +0200,
> > > Andy Shevchenko <andriy.shevchenko@linux.intel.com> a écrit :
> > > > On Fri, Mar 18, 2022 at 05:00:47PM +0100, Clément Léger wrote:

...

> > > > > + values = kcalloc(nval, sizeof(*values), GFP_KERNEL);
> > > > > + if (!values)
> > > > > + return -ENOMEM;
> > > > > +
> > > > > + ret = fwnode_property_read_string_array(fwnode, propname, values, nval);
> > > > > + if (ret < 0)
> > > > > + goto out;
> > > > > +
> > > > > + *string = values[index];
> > > > > +out:
> > > > > + kfree(values);
> > > >
> > > > Here is UAF (use after free). How is it supposed to work?
> > >
> > > values is an array of pointers. I'm only retrieving a pointer out of
> > > it.
> >
> > I see, thanks for pointing out.
> >
> > Nevertheless, I don't like the idea of allocating memory in this case.
> > Can we rather add a new callback that will provide us the necessary
> > property directly?
> >
>
> IMHO, it would indeed be better. However,
> fwnode_property_match_string() also allocates memory to do the same
> kind of operation. Would you also like a callback for this one ?

But matching string will need all of them to cover all possible cases.
So, it doesn't rely on the certain index and needs allocation anyway.

--
With Best Regards,
Andy Shevchenko


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