Re: [PATCH bpf-next 1/2] bpf: Mark tracing_multi trampolines as ftrace managed

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, Jul 10, 2026 at 10:47:33PM +0800, Leon Hwang wrote:
> Since tracing_multi link does not set ftrace_managed, it would fail to
> release the tracing_multi link when attaching tracing_multi link and
> then attaching fentry link.
> 
> [    3.714215] WARNING: kernel/bpf/trampoline.c:1727 at bpf_trampoline_multi_detach+0x20b/0x240, CPU#1: test_progs/97
> ...
> [    3.733170]  bpf_tracing_multi_link_release+0x14/0x30
> [    3.733890]  bpf_link_free+0x58/0x130
> [    3.734414]  bpf_link_release+0x23/0x30
> 
> Fix it by setting 'ftrace_managed = true' in register_fentry_multi().
> 
> Fixes: aef4dfa790b2 ("bpf: Add bpf_trampoline_multi_attach/detach functions")
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
>  kernel/bpf/trampoline.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 1a721fc4bef5..6eadf64f7ec9 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -1536,6 +1536,7 @@ static int register_fentry_multi(struct bpf_trampoline *tr, struct bpf_tramp_ima
>  	if (bpf_trampoline_use_jmp(tr->flags))
>  		addr = ftrace_jmp_set(addr);
>  
> +	tr->func.ftrace_managed = true;

I wonder we could set tr->func.ftrace_managed early in bpf_trampoline_get,
but we could do that as follow up

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka


>  	ftrace_hash_add(data->reg, data->entry, ip, addr);
>  	tr->cur_image = im;
>  	return 0;
> -- 
> 2.55.0
>