In the Linux kernel, the following vulnerability has been resolved: btrfs: fix lockdep splat and potential deadlock after failure running delayed items When running delayed items we are holding a delayed node's mutex and then we will attempt to modify a subvolume btree to insert/update/delete the delayed items. However if have an error during the insertions for example, btrfs_insert_delayed_items() may return with a path that has locked extent buffers (a leaf at the very least), and then we attempt to release the delayed node at __btrfs_run_delayed_items(), which requires taking the delayed node's mutex, causing an ABBA type of deadlock. This was reported by syzbot and the lockdep splat is the following: WARNING: possible circular locking dependency detected 6.5.0-rc7-syzkaller-0002