Re: [PATCHv5 bpf-next 20/28] libbpf: Add support to create tracing multi link

[bot+bpf-ci@kernel.org]

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> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 49368ee161b1..9bf7e8754c7b 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c

[ ... ]

> @@ -12510,6 +12592,197 @@ bool btf_type_is_traceable_func(const struct btf *btf, const struct btf_type *t
>  	return true;
>  }
>
> +static int collect_func_ids_by_glob(const struct bpf_program *prog, const char *pattern, __u32 **ids)
> +{
> +	struct bpf_object *obj = prog->obj;
> +	const struct module_btf *mod;
> +	struct btf *btf = NULL;
> +	const char *sep;
> +	int err;
> +
> +	err = bpf_object__load_vmlinux_btf(obj, true);
> +	if (err)
> +		return err;
> +
> +	/* In case we have module specified, we will find its btf and use that. */
> +	sep = strchr(pattern, ':');
> +	if (sep) {
> +		mod = find_attach_module(obj, pattern);
> +		if (!mod) {
> +			err = -EINVAL;
> +			goto cleanup;
> +		}
> +		btf = mod->btf;
> +		pattern = sep + 1;
> +	} else {
> +		/* Program is loaded for kernel module. */
> +		if (prog->attach_btf_obj_fd)
> +			return -EINVAL;
> +		btf = obj->btf_vmlinux;
> +	}
> +
> +	err = collect_btf_func_ids_by_glob(btf, pattern, ids);
> +
> +cleanup:
> +	bpf_object_cleanup_btf(obj);
> +	return err;
> +}

Does this function leak the vmlinux BTF when prog->attach_btf_obj_fd is
set? The early return bypasses the cleanup label that calls
bpf_object_cleanup_btf(obj). Every other error path goes through
cleanup, which suggests the BTF loaded by bpf_object__load_vmlinux_btf()
needs to be cleaned up before returning.

The design pattern here is that bpf_object__load_vmlinux_btf(obj, true)
is called specifically at attach-time (after the object has already been
post-load-cleaned), so obj->btf_vmlinux is freshly loaded. Skipping the
cleanup leaves that freshly-loaded btf_vmlinux attached to the bpf_object
until bpf_object__close().

Should this be 'err = -EINVAL; goto cleanup;' to match the other error
paths?

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/24598000047