Skip to contentSkip to conversation

FAILED: patch "[PATCH] btrfs: fix a block group ref counter leak after failure to" failed to apply to 4.19-stable tree

PATCH [email protected] 2 participants 2 messages Jun 29, 2020 – Jul 2, 2020

Subsystems (2)
Stable branch Btrfs file system
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9fecd13202f520f3f25d5b1c313adb740fe19773 Mon Sep 17 00:00:00 2001
From: Filipe Manana <[email protected]>
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 [email protected] # 4.4+
Reviewed-by Nikolay Borisov <[email protected]>
Reviewed-by Anand Jain <[email protected]>
Signed-off-by Filipe Manana <[email protected]>
Reviewed-by David Sterba <[email protected]>
Signed-off-by David Sterba <[email protected]>
fs/btrfs/block-group.c +9 -10
index 176e8a292fd1..6462dd0b155c 100644
@@ -940,7 +940,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 	path = btrfs_alloc_path();
 	if (!path) {
 		ret = -ENOMEM;
-		goto out_put_group;
+		goto out;
 	}
 
 	/*

@@ -978,7 +978,7 @@ 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 */

@@ -1001,13 +1001,13 @@ 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);
 	}
 

@@ -1016,6 +1016,9 @@ 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);

@@ -1125,10 +1128,7 @@ 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 = remove_block_group_item(trans, path, block_group);
 	if (ret < 0)

@@ -1145,10 +1145,9 @@ 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);
maintainer
#1 lore raw
Quoted 40 lines · On Mon, Jun 29, 2020 at 01:00:43PM +0200, [email protected] 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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9fecd13202f520f3f25d5b1c313adb740fe19773 Mon Sep 17 00:00:00 2001
From: Filipe Manana <[email protected]>
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'.

Quoted 7 lines
Fixes f6033c5e333238 ("btrfs: fix block group leak when removing fails")
CC [email protected] # 4.4+
Reviewed-by Nikolay Borisov <[email protected]>
Reviewed-by Anand Jain <[email protected]>
Signed-off-by Filipe Manana <[email protected]>
Reviewed-by David Sterba <[email protected]>
Signed-off-by David Sterba <[email protected]>

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.

Signature · 2 lines
Thanks,
Sasha