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

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: libbpf: Prevent null-pointer dereference when prog to load has no BTF In bpf_objec_load_prog(), there's no guarantee that obj->btf is non-NULL when passing it to btf__fd(), and this function does not perform any check before dereferencing its argument (as bpf_object__btf_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 btf__fd() in the fix instead of reverting to bpf_object__btf_fd().

References

• https://git.kernel.org/stable/c/ef80b59acfa4dee4b5eaccb15572b69248831104
• https://git.kernel.org/stable/c/1fd91360a75833b7110af9834ae26c977e1273e0
• https://git.kernel.org/stable/c/9bf48fa19a4b1d186e08b20bf7e5de26a15644fb