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    Subject[PATCH 5.7 058/265] btrfs: fix a block group ref counter leak after failure to remove block group
    Date
    From: Filipe Manana <fdmanana@suse.com>

    [ Upstream commit 9fecd13202f520f3f25d5b1c313adb740fe19773 ]

    When removing a block group, if we fail to delete the block group's item
    from the extent tree, we jump to the 'out' label and end up decrementing
    the block group's reference count once only (by 1), resulting in a counter
    leak because the block group at that point was already removed from the
    block group cache rbtree - so we have to decrement the reference count
    twice, once for the rbtree and once for our lookup at the start of the
    function.

    There is a second bug where if removing the free space tree entries (the
    call to remove_block_group_free_space()) fails we end up jumping to the
    'out_put_group' label but end up decrementing the reference count only
    once, when we should have done it twice, since we have already removed
    the block group from the block group cache rbtree. This happens because
    the reference count decrement for the rbtree reference happens after
    attempting to remove the free space tree entries, which is far away from
    the place where we remove the block group from the rbtree.

    To make things less error prone, decrement the reference count for the
    rbtree immediately after removing the block group from it. This also
    eleminates the need for two different exit labels on error, renaming
    'out_put_label' to just 'out' and removing the old 'out'.

    Fixes: f6033c5e333238 ("btrfs: fix block group leak when removing fails")
    CC: stable@vger.kernel.org # 4.4+
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Reviewed-by: Anand Jain <anand.jain@oracle.com>
    Signed-off-by: Filipe Manana <fdmanana@suse.com>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/btrfs/block-group.c | 19 +++++++++----------
    1 file changed, 9 insertions(+), 10 deletions(-)

    diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
    index 233c5663f2332..0c17f18b47940 100644
    --- a/fs/btrfs/block-group.c
    +++ b/fs/btrfs/block-group.c
    @@ -916,7 +916,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
    path = btrfs_alloc_path();
    if (!path) {
    ret = -ENOMEM;
    - goto out_put_group;
    + goto out;
    }

    /*
    @@ -954,7 +954,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
    ret = btrfs_orphan_add(trans, BTRFS_I(inode));
    if (ret) {
    btrfs_add_delayed_iput(inode);
    - goto out_put_group;
    + goto out;
    }
    clear_nlink(inode);
    /* One for the block groups ref */
    @@ -977,13 +977,13 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,

    ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
    if (ret < 0)
    - goto out_put_group;
    + goto out;
    if (ret > 0)
    btrfs_release_path(path);
    if (ret == 0) {
    ret = btrfs_del_item(trans, tree_root, path);
    if (ret)
    - goto out_put_group;
    + goto out;
    btrfs_release_path(path);
    }

    @@ -992,6 +992,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
    &fs_info->block_group_cache_tree);
    RB_CLEAR_NODE(&block_group->cache_node);

    + /* Once for the block groups rbtree */
    + btrfs_put_block_group(block_group);
    +
    if (fs_info->first_logical_byte == block_group->start)
    fs_info->first_logical_byte = (u64)-1;
    spin_unlock(&fs_info->block_group_cache_lock);
    @@ -1102,10 +1105,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,

    ret = remove_block_group_free_space(trans, block_group);
    if (ret)
    - goto out_put_group;
    -
    - /* Once for the block groups rbtree */
    - btrfs_put_block_group(block_group);
    + goto out;

    ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
    if (ret > 0)
    @@ -1128,10 +1128,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
    free_extent_map(em);
    }

    -out_put_group:
    +out:
    /* Once for the lookup reference */
    btrfs_put_block_group(block_group);
    -out:
    if (remove_rsv)
    btrfs_delayed_refs_rsv_release(fs_info, 1);
    btrfs_free_path(path);
    --
    2.25.1
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