[PATCH 4.9 52/64] btrfs: fix NULL pointer dereference from free_reloc_roots()

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naohiro Aota <naohiro.a...@wdc.com>

commit bb166d7207432d3c7d10c45dc052f12ba3a2121d upstream.

__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")
Signed-off-by: Naohiro Aota <naohiro.a...@wdc.com>
Reviewed-by: Nikolay Borisov <nbori...@suse.com>
Reviewed-by: David Sterba <dste...@suse.com>
Signed-off-by: David Sterba <dste...@suse.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/btrfs/relocation.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2367,11 +2367,11 @@ void free_reloc_roots(struct list_head *
        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);
        }
 }