linux-kernel - [PATCH 5.11 638/775] btrfs: fix reloc root leak with 0 ref reloc roots on recovery

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Message-Id: <20210301161232.923584167@linuxfoundation.org>
Date:   Mon,  1 Mar 2021 17:13:26 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.11 638/775] btrfs: fix reloc root leak with 0 ref reloc roots on recovery

From: Josef Bacik <josef@...icpanda.com>

commit c78a10aebb275c38d0cfccae129a803fe622e305 upstream.

When recovering a relocation, if we run into a reloc root that has 0
refs we simply add it to the reloc_control->reloc_roots list, and then
clean it up later.  The problem with this is __del_reloc_root() doesn't
do anything if the root isn't in the radix tree, which in this case it
won't be because we never call __add_reloc_root() on the reloc_root.

This exit condition simply isn't correct really.  During normal
operation we can remove ourselves from the rb tree and then we're meant
to clean up later at merge_reloc_roots() time, and this happens
correctly.  During recovery we're depending on free_reloc_roots() to
drop our references, but we're short-circuiting.

Fix this by continuing to check if we're on the list and dropping
ourselves from the reloc_control root list and dropping our reference
appropriately.  Change the corresponding BUG_ON() to an ASSERT() that
does the correct thing if we aren't in the rb tree.

CC: stable@...r.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@...icpanda.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/relocation.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -668,9 +668,7 @@ static void __del_reloc_root(struct btrf
 			RB_CLEAR_NODE(&node->rb_node);
 		}
 		spin_unlock(&rc->reloc_root_tree.lock);
-		if (!node)
-			return;
-		BUG_ON((struct btrfs_root *)node->data != root);
+		ASSERT(!node || (struct btrfs_root *)node->data == root);
 	}

 	/*