btrfs in the Linux kernel before 5.13.4 allows attackers to cause a denial of service (deadlock) via processes that trigger allocation of new system chunks during times when there is a shortage of free space in the system space_info.
https://security.netapp.com/advisory/ntap-20210902-0010/
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.13.4