Re: [PATCH bpf-next 2/2] bpf: Check link_create parameter for multi_uprobe

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Mar 31, 2025 at 05:47:45PM +0800, Tao Chen wrote:
> The target_fd and flags in link_create no used in multi_uprobe
> , return -EINVAL if they assigned, keep it same as other link
> attach apis.
> 
> Fixes: 89ae89f53d20 ("bpf: Add multi uprobe link")
> Signed-off-by: Tao Chen <chen.dylane@linux.dev>
> ---
>  kernel/trace/bpf_trace.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 2f206a2a2..f7ebf17e3 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3385,6 +3385,9 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
>  	if (sizeof(u64) != sizeof(void *))
>  		return -EOPNOTSUPP;
>  
> +	if (attr->link_create.target_fd || attr->link_create.flags)
> +		return -EINVAL;

I think the CI is failing because usdt code does uprobe multi detection
with target_fd = -1 and it fails and perf-uprobe fallback will fail on
not having enough file descriptors

but I think at this stage we will brake some user apps by introducing
this check, link ebpf go library, which passes 0

jirka


> +
>  	if (!is_uprobe_multi(prog))
>  		return -EINVAL;
>  
> -- 
> 2.43.0
>