Re: [PATCH 1/6] property: add fwnode_property_read_string_index()

Le Fri, 18 Mar 2022 20:09:37 +0200,
Andy Shevchenko [off-list ref] a écrit :

On Fri, Mar 18, 2022 at 05:49:12PM +0100, Clément Léger wrote:

quoted

Le Fri, 18 Mar 2022 18:26:00 +0200,
Andy Shevchenko [off-list ref] a écrit :  

quoted

On Fri, Mar 18, 2022 at 05:00:47PM +0100, Clément Léger wrote:  

quoted

Add fwnode_property_read_string_index() function which allows to
retrieve a string from an array by its index. This function is the
equivalent of of_property_read_string_index() but for fwnode support.    

...

quoted

quoted

quoted

+	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 ?

Thanks,

-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com