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.
Thanks,
Arne
>
> + logical >> PAGE_CACHE_SHIFT, 1);
> + if (ret == 1)
> + kref_get(&zone->refcnt);
> }
> + spin_unlock(&fs_info->reada_lock);
>
> return zone;
> }
>
> regards,
> dan carpenter
>
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