bpf: Handle return value of ftrace_set_filter_ip in register_fentry

The error that returned by ftrace_set_filter_ip() in register_fentry() is
not handled properly. Just fix it.

Fixes: 00963a2 ("bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)")
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20251110120705.1553694-1-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: image-dragon

kernel/bpf/trampoline.c

@@ -220,7 +220,9 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 	}
 
 	if (tr->func.ftrace_managed) {
-		ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
+		ret = ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
+		if (ret)
+			return ret;
 		ret = register_ftrace_direct(tr->fops, (long)new_addr);
 	} else {
 		ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);