bpf: prevent leak of lsm program after failed attach

Vulnerability Description

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/

References

• https://git.kernel.org/stable/c/82b39df5ddb298daaf6dc504032ff7eb027fa106
• https://git.kernel.org/stable/c/6a1504dd36cd9a0a69250d61da8bdb17b29f1fe8
• https://git.kernel.org/stable/c/e89f3edffb860a0f54a9ed16deadb7a4a1fa3862