[PATCH 5.8 041/232] btrfs: check correct variable after allocation in btrfs_backref_iter_alloc

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Boleyn Su <boleynsu@xxxxxxxxxx>

commit c15c2ec07a26b251040943a1a9f90d3037f041e5 upstream.

The `if (!ret)` check will always be false and it may result in
ret->path being dereferenced while it is a NULL pointer.

Fixes: a37f232b7b65 ("btrfs: backref: introduce the skeleton of btrfs_backref_iter")
CC: stable@xxxxxxxxxxxxxxx # 5.8+
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: Boleyn Su <boleynsu@xxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/backref.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -2303,7 +2303,7 @@ struct btrfs_backref_iter *btrfs_backref
 		return NULL;
 
 	ret->path = btrfs_alloc_path();
-	if (!ret) {
+	if (!ret->path) {
 		kfree(ret);
 		return NULL;
 	}