bpf: prevent leak of lsm program after failed attach

In the Linux kernel, the following vulnerability has been resolved: bpf: prevent leak of lsm program after failed attach In [0], we added the ability to bpf_prog_attach LSM programs to cgroups, but in our validation to make sure the prog is meant to be attached to BPF_LSM_CGROUP, we return too early if the check fails. This results in lack of decrementing prog's refcnt (through bpf_prog_put) leaving the LSM program alive past the point of the expected lifecycle. This fix allows for the decrement to take place. [0] https://lore.kernel.org/all/20220628174314.1216643-4-sdf@google.com/