CVE-2024-38574

In the Linux kernel, the following vulnerability has been resolved:

libbpf: Prevent null-pointer dereference when prog to load has no BTF

In bpfobjecload_prog(), there's no guarantee that obj->btf is non-NULL when passing it to btffd(), and this function does not perform any check before dereferencing its argument (as bpf_objectbtf_fd() used to do). As a consequence, we get segmentation fault errors in bpftool (for example) when trying to load programs that come without BTF information.

v2: Keep btffd() in the fix instead of reverting to bpf_objectbtf_fd().