bpf,lsm: Drop bpf_prog_free from sleepable_lsm_hooks

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf,lsm: Drop bpf_prog_free from sleepable_lsm_hooks __bpf_prog_put_rcu() is the call_rcu() callback for non-sleepable programs. security_bpf_prog_free() called from there fires bpf_prog_free in softirq; if a sleepable LSM prog is attached to that hook, might_fault() BUGs: BUG: sleeping function called from invalid context in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5038 preempt_count: 101, expected: 0 Call Trace: <IRQ> __bpf_prog_enter_sleepable+0x1cd/0x320 kernel/bpf/trampoline.c:1255 bpf_trampoline_6442549705+0x53/0xd7 security_bpf_prog_free+0xde/0x130 security/security.c:5465 __bpf_prog_put_rcu+0xab/0xd0 kernel/bpf/syscall.c:2365 rcu_do_batch kernel/rcu/tree.c:2617 [inline] handle_softirqs+0x236/0x800 kernel/softirq.c:622 </IRQ> The call_rcu/call_rcu_tasks_trace split reflects the freed program's sleepability, not that of any attached observer. security_bpf_prog_free() also frees prog->aux->security, which has to stay after the grace period, so drop bpf_prog_free from sleepable_lsm_hooks rather than move the call. Non-sleepable observers still run there.