bpf: Avoid __bpf_prog_ret0_warn when jit fails

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

bpf: Avoid __bpf_prog_ret0_warn when jit fails

syzkaller reported an issue:

WARNING: CPU: 3 PID: 217 at kernel/bpf/core.c:2357 __bpf_prog_ret0_warn+0xa/0x20 kernel/bpf/core.c:2357

Modules linked in:

CPU: 3 UID: 0 PID: 217 Comm: kworker/u32:6 Not tainted 6.15.0-rc4-syzkaller-00040-g8bac8898fe39

RIP: 0010:__bpf_prog_ret0_warn+0xa/0x20 kernel/bpf/core.c:2357

Call Trace:

<TASK>

bpf_dispatcher_nop_func include/linux/bpf.h:1316 [inline]

__bpf_prog_run include/linux/filter.h:718 [inline]

bpf_prog_run include/linux/filter.h:725 [inline]

cls_bpf_classify+0x74a/0x1110 net/sched/cls_bpf.c:105

...

When creating bpf program, 'fp->jit_requested' depends on bpf_jit_enable.

This issue is triggered because of CONFIG_BPF_JIT_ALWAYS_ON is not set

and bpf_jit_enable is set to 1, causing the arch to attempt JIT the prog,

but jit failed due to FAULT_INJECTION. As a result, incorrectly

treats the program as valid, when the program runs it calls

`__bpf_prog_ret0_warn` and triggers the WARN_ON_ONCE(1).