CVE-2025-21728: Undefined Security Weakness

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

bpf: Send signals asynchronously if !preemptible

BPF programs can execute in all kinds of contexts and when a program running in a non-preemptible context uses the bpf_send_signal() kfunc, it will cause issues because this kfunc can sleep. Change `irqs_disabled()` to `!preemptible()`.