On Mon, Apr 30, 2012 at 01:23:29PM +0200, Arne Jansen wrote:
> On 30.04.2012 13:11, Dan Carpenter wrote:
> > Hello Arne Jansen,
> >
> > The patch 8c9c2bf7a3c4: "btrfs: fix race in reada" from Feb 25, 2012,
> > leads to the following warning:
> > fs/btrfs/reada.c:308 reada_find_zone()
> > warn: 'zone' was already freed.
>
> Who emits this warning? It's bogus.
>
> >
> > @@ -307,13 +302,15 @@ again:
> > ret = radix_tree_insert(&dev->reada_zones,
> > (unsigned long)(zone->end >>
> > PAGE_CACHE_SHIFT),
> > zone);
> > - spin_unlock(&fs_info->reada_lock);
> >
> > - if (ret) {
> > + if (ret == -EEXIST) {
> > kfree(zone);
> > ^^^^^^^^^^^
> > Freed here.
> >
> > - looped = 1;
> > - goto again;
> > + ret = radix_tree_gang_lookup(&dev->reada_zones, (void
> > **)&zone,
> >
> > ^^^^
> > Use after free inside radix_tree_gang_lookup() function.
>
> It's not used by radix_tree_gang_lookup, the second parameter is
> a pointer to the return value.
Ah. We can only write one item, because we pass max_items = 1.
Nevermind. The code in reada.c is fine. Sorry for the noise.
regards,
dan carpenter
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