Re: [PATCH 17/17] mtd: rawnand: nandsim: Reorganize ns_cleanup_module()

[Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>]

On Mon, 25 May 2020 00:13:28 +0200
Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:

> Hi Richard,
> 
> Richard Weinberger <richard.weinberger@xxxxxxxxx> wrote on Sun, 24 May
> 2020 23:37:13 +0200:
> 
> > On Sat, May 9, 2020 at 9:19 PM Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:  
> > >         ns_debugfs_remove(ns);
> > > -       ns_free(ns);    /* Free nandsim private resources */
> > > -       nand_release(chip); /* Unregister driver */
> > > -       kfree(ns);        /* Free other structures */
> > > -       ns_free_lists();
> > > +       WARN_ON(mtd_device_unregister(nsmtd));
> > > +       ns_free(ns);
> > > +       kfree(erase_block_wear);
> > > +       nand_cleanup(chip);
> > > +       list_for_each_safe(pos, n, &grave_pages) {
> > > +               kfree(list_entry(pos, struct grave_page, list));
> > > +               list_del(pos);    
> > 
> > Are you sure you can use pos after freeing the entry?
> > Smells like use after free.
> >   
> 
> Mmmmh, I should probably invert those two lines, first call list_del()
> and then call kfree() on list_entry().

You can also use  list_for_each_entry_safe():

	struct grave_page *pos, *n;

	...

	list_for_each_safe(pos, n, &grave_pages, list) {
		list_del(&pos->list);
		kfree(pos);
	}

> 
> Thanks for noticing!
> Miquèl


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