In kernel/bpf/hashtab.c in the Linux kernel through 5.13.8, there is an integer overflow and out-of-bounds write when many elements are placed in a single bucket. NOTE: exploitation might be impractical without the CAP_SYS_ADMIN capability.
https://www.debian.org/security/2021/dsa-4978
https://security.netapp.com/advisory/ntap-20210909-0001/
https://lore.kernel.org/bpf/20210806150419.109658-1-th.yasumatsu%40gmail.com/