On Mon, Jun 29, 2020 at 01:00:43PM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 9fecd13202f520f3f25d5b1c313adb740fe19773 Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@xxxxxxxx>
Date: Mon, 1 Jun 2020 19:12:06 +0100
Subject: [PATCH] btrfs: fix a block group ref counter leak after failure to
remove block group
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@xxxxxxxxxxxxxxx # 4.4+
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
On older branches, btrfs_remove_block_group() lived in
fs/btrfs/extent-tree.c. I've fixed up the patch and queued it for
4.19-4.9. The 4.4 backport needs some attention.
--
Thanks,
Sasha
