[PATCH] btrfs: add missing NULL check in btrfs_free_tree_block()

[Riyan Dhiman <riyandhiman14@gmail.com>]

In commit 3ba2d3648f9dc (btrfs: reflow btrfs_free_tree_block), the block
group lookup using btrfs_lookup_block_group() was added in btrfs_free_tree_block().
However, the return value of this function is not checked for a NULL result,
which can lead to null pointer dereferences if the block group is not found.

This patch adds a check to ensure that if btrfs_lookup_block_group() returns
NULL, the function will gracefully exit, preventing further operations that
rely on a valid block group pointer.

Signed-off-by: Riyan Dhiman <riyandhiman14@gmail.com>
---
Compile tested only

 fs/btrfs/extent-tree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a5966324607d..7782d4436ca0 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3454,6 +3454,8 @@ int btrfs_free_tree_block(struct btrfs_trans_handle *trans,
 	}
 
 	bg = btrfs_lookup_block_group(fs_info, buf->start);
+	if (!bg)
+		goto out;
 
 	if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
 		pin_down_extent(trans, bg, buf->start, buf->len, 1);
-- 
2.46.1