On Thu, Mar 05, 2026 at 02:59:48PM +0800, Leon Hwang wrote:
SNIP
> > +static int tracing_multi_mod_fd(struct bpf_program *prog, int *btf_obj_fd)
> > +{
> > + const char *attach_name, *sep, *mod_name = NULL;
> > + int i, err, mod_len = 0;
> > +
> > + *btf_obj_fd = 0;
> > + attach_name = strchr(prog->sec_name, '/');
> > +
> > + /* Program with no details in spec, using kernel btf. */
> > + if (!attach_name)
> > + return 0;
> > +
> > + attach_name++;
> > + sep = strchr(attach_name, ':');
> > + if (sep) {
> > + mod_name = attach_name;
> > + mod_len = sep - mod_name;
> > + }
> > +
> > + /* Program with no module section, using kernel btf. */
> > + if (!mod_name)
> > + return 0;
> > +
> > + err = load_module_btfs(prog->obj);
> > + if (err)
> > + return err;
> > +
> > + for (i = 0; i < prog->obj->btf_module_cnt; i++) {
> > + const struct module_btf *mod = &prog->obj->btf_modules[i];
> > +
> > + if (mod_name && strncmp(mod->name, mod_name, mod_len) == 0) {
>
> strncmp() is not enough to exactly compare two module names, as
> strncmp() only compares the first 'mod_len' bytes.
>
> So, mod_name "foo" could match mod "foobar", since 'obj->btf_modules'
> are not sorted by name after loading from kernel.
>
> To find the exact module via module name, "strncmp() == 0 &&
> mod->name[mod_len] == '\0'" would be better.
yes, good catch, will fix
SNIP
> > +static int collect_func_ids_by_glob(struct bpf_object *obj, const char
> > *pattern, __u32 **ids)
> > +{
> > + const char *mod_name = NULL, *sep;
> > + int i, err, mod_len = 0;
> > + struct btf *btf = NULL;
> > +
> > + 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_name = pattern;
> > + mod_len = sep - pattern;
> > + pattern = sep + 1;
> > +
> > + err = load_module_btfs(obj);
> > + if (err)
> > + goto cleanup;
> > +
> > + for (i = 0; i < obj->btf_module_cnt; i++) {
> > + const struct module_btf *mod = &obj->btf_modules[i];
> > +
> > + if (!strncmp(mod->name, mod_name, mod_len)) {
>
> Same concern here.
>
> Would it be better to factor out a helper to find module via name?
we have similar issue in find_kernel_btf_id, but we get away with
that with just continuing to loop modules if the lookup fails
I agree some helper would be good hear, will try to add it
thanks,
jirka
