btrfs: fix NULL pointer dereference from free_reloc_roots()

__del_reloc_root should be called before freeing up reloc_root->node.
If not, calling __del_reloc_root() dereference reloc_root->node, causing
the system BUG.

Fixes: 6bdf131fac23 ("Btrfs: don't leak reloc root nodes on error")
Cc: <stable@vger.kernel.org> # 4.9
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3a49a3c..9841fae 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2400,11 +2400,11 @@ void free_reloc_roots(struct list_head *list)
        while (!list_empty(list)) {
                reloc_root = list_entry(list->next, struct btrfs_root,
                                        root_list);
+               __del_reloc_root(reloc_root);
                free_extent_buffer(reloc_root->node);
                free_extent_buffer(reloc_root->commit_root);
                reloc_root->node = NULL;
                reloc_root->commit_root = NULL;
-               __del_reloc_root(reloc_root);
        }
 }