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btrfs: fix block group leak when removing fails 

btrfs_remove_block_group() invokes btrfs_lookup_block_group(), which
returns a local reference of the block group that contains the given
bytenr to "block_group" with increased refcount.

When btrfs_remove_block_group() returns, "block_group" becomes invalid,
so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in several exception handling paths
of btrfs_remove_block_group(). When those error scenarios occur such as
btrfs_alloc_path() returns NULL, the function forgets to decrease its
refcnt increased by btrfs_lookup_block_group() and will cause a refcnt
leak.

Fix this issue by jumping to "out_put_group" label and calling
btrfs_put_block_group() when those error scenarios occur.

CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
alistair/sensors
Xiyu Yang 2020-04-21 10:54:11 +08:00 committed by David Sterba
parent ef67963dac
commit f6033c5e33
1 changed files with 10 additions and 6 deletions
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16
fs/btrfs/block-group.c
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@ -916,7 +916,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
path = btrfs_alloc_path();
if (!path) {
ret = -ENOMEM;
goto out;
goto out_put_group;
}
/*
@ -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;
goto out_put_group;
}
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;
goto out_put_group;
if (ret > 0)
btrfs_release_path(path);
if (ret == 0) {
ret = btrfs_del_item(trans, tree_root, path);
if (ret)
goto out;
goto out_put_group;
btrfs_release_path(path);
}
@ -1102,9 +1102,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
ret = remove_block_group_free_space(trans, block_group);
if (ret)
goto out;
goto out_put_group;
btrfs_put_block_group(block_group);
/* Once for the block groups rbtree */
btrfs_put_block_group(block_group);
ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
@ -1127,6 +1127,10 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
/* once for the tree */
free_extent_map(em);
}
out_put_group:
/* Once for the lookup reference */
btrfs_put_block_group(block_group);
out:
if (remove_rsv)
btrfs_delayed_refs_rsv_release(fs_info, 1);