A use-after-free flaw was found in btf_dump_name_dups in tools/lib/bpf/btf_dump.c in libbpf in the Linux Kernel. This issue occurs because the key stored in the hash table name_map is a string address, and the string memory is allocated by realloc() function. When the memory is resized by realloc() later, the old memory may be freed.

Mitigation

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.

For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:

cat /proc/sys/kernel/unprivileged_bpf_disabled

The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.