From 2abc726ab4b83db774e315c660ab8da21477092f Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Wed, 4 Mar 2020 11:18:24 -0500 Subject: btrfs: do not init a reloc root if we aren't relocating We previously were checking if the root had a dead root before accessing root->reloc_root in order to avoid a use-after-free type bug. However this scenario happens after we've unset the reloc control, so we would have been saved if we'd simply checked for fs_info->reloc_control. At this point during relocation we no longer need to be creating new reloc roots, so simply move this check above the reloc_root checks to avoid any future races and confusion. Reviewed-by: Qu Wenruo Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/relocation.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'fs/btrfs') diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index d2069d69fc92..631f94085ba6 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1511,6 +1511,10 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, int clear_rsv = 0; int ret; + if (!rc || !rc->create_reloc_tree || + root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) + return 0; + /* * The subvolume has reloc tree but the swap is finished, no need to * create/update the dead reloc tree @@ -1524,10 +1528,6 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, return 0; } - if (!rc || !rc->create_reloc_tree || - root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) - return 0; - if (!trans->reloc_reserved) { rsv = trans->block_rsv; trans->block_rsv = rc->block_rsv; @@ -2369,6 +2369,18 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc, trans = NULL; goto out; } + + /* + * At this point we no longer have a reloc_control, so we can't + * depend on btrfs_init_reloc_root to update our last_trans. + * + * But that's ok, we started the trans handle on our + * corresponding fs_root, which means it's been added to the + * dirty list. At commit time we'll still call + * btrfs_update_reloc_root() and update our root item + * appropriately. + */ + reloc_root->last_trans = trans->transid; trans->block_rsv = rc->block_rsv; replaced = 0; -- cgit