An issue was discovered in the Linux kernel through 5.6.11. btree_gc_coalesce in drivers/md/bcache/btree.c has a deadlock if a coalescing operation fails.
https://www.oracle.com/security-alerts/cpuApr2021.html
https://usn.ubuntu.com/4485-1/
https://usn.ubuntu.com/4483-1/
https://usn.ubuntu.com/4465-1/
https://usn.ubuntu.com/4463-1/
https://usn.ubuntu.com/4462-1/
https://security.netapp.com/advisory/ntap-20200608-0001/
https://lkml.org/lkml/2020/4/26/87
https://lists.debian.org/debian-lts-announce/2020/10/msg00034.html
https://lists.debian.org/debian-lts-announce/2020/10/msg00032.html
https://lists.debian.org/debian-lts-announce/2020/08/msg00019.html
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00009.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00071.html