On Fri, May 2, 2025 at 11:26 PM Peter Zijlstra <pet...@infradead.org> wrote:
>
> Designate the "module:${modname}" symbol namespace to mean: 'only
> export to the named module'.
>
> Notably, explicit imports of anything in the "module:" space is
> forbidden.
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> ---
> kernel/module/main.c | 33 +++++++++++++++++++++++++++++++--
> scripts/mod/modpost.c | 11 ++++++++++-
> 2 files changed, 41 insertions(+), 3 deletions(-)
>
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -1083,6 +1083,14 @@ static char *get_modinfo(const struct lo
> return get_next_modinfo(info, tag, NULL);
> }
>
> +static bool verify_module_namespace(const char *namespace, const char
> *modname)
> +{
> + const char *prefix = "module:";
> +
> + return strstarts(namespace, prefix) &&
> + !strsmp(namespace + strlen(prefix), modname);
> +}
> +
> static int verify_namespace_is_imported(const struct load_info *info,
> const struct kernel_symbol *sym,
> struct module *mod)
> @@ -1092,6 +1100,10 @@ static int verify_namespace_is_imported(
>
> namespace = kernel_symbol_namespace(sym);
> if (namespace && namespace[0]) {
> +
> + if (verify_module_namespace(namespace, mod->name))
> + return 0;
> +
> for_each_modinfo_entry(imported_namespace, info, "import_ns")
> {
> if (strcmp(namespace, imported_namespace) == 0)
> return 0;
> @@ -1659,15 +1671,30 @@ static void module_license_taint_check(s
> }
> }
>
> -static void setup_modinfo(struct module *mod, struct load_info *info)
> +static int setup_modinfo(struct module *mod, struct load_info *info)
> {
> const struct module_attribute *attr;
> + char *imported_namespace;
> int i;
>
> for (i = 0; (attr = modinfo_attrs[i]); i++) {
> if (attr->setup)
> attr->setup(mod, get_modinfo(info, attr->attr.name));
> }
> +
> + for_each_modinfo_entry(imported_namespace, info, "import_ns") {
> + /*
> + * 'module:' prefixed namespaces are implicit, disallow
> + * explicit imports.
> + */
> + if (strstarts(imported_namespace, "module:")) {
> + pr_err("%s: module tries to import module namespace:
> %s\n",
> + mod->name, imported_namespace);
> + return -EPERM;
> + }
It is also possible to check this at compile-time, i.e., in modpost.
Does it make sense to check this at compile-time instead of
run-time?
(or check it both at compile-time and build-time?)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index c9ff4db26edb..30c8d8062792 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1597,9 +1597,14 @@ static void read_symbols(const char *modname)
for (namespace = get_modinfo(&info, "import_ns");
namespace;
- namespace = get_next_modinfo(&info, "import_ns",
namespace))
+ namespace = get_next_modinfo(&info, "import_ns",
namespace)) {
+ if (strstarts(namespace, "module:"))
+ error("%s: tries to import module
namespace \"%s\".\n");
+
add_namespace(&mod->imported_namespaces, namespace);
+ }
+
if (!get_modinfo(&info, "description"))
warn("missing MODULE_DESCRIPTION() in %s\n", modname);
}
> + }
> +
> + return 0;
> }
>
> static void free_modinfo(struct module *mod)
> @@ -3335,7 +3362,9 @@ static int load_module(struct load_info
> goto free_unload;
>
> /* Set up MODINFO_ATTR fields */
> - setup_modinfo(mod, info);
> + err = setup_modinfo(mod, info);
> + if (err)
> + goto free_modinfo;
>
> /* Fix up syms, so that st_value is a pointer to location. */
> err = simplify_symbols(mod, info);
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1682,6 +1682,14 @@ void buf_write(struct buffer *buf, const
> buf->pos += len;
> }
>
> +static bool verify_module_namespace(const char *namespace, const char
> *modname)
> +{
> + const char *prefix = "module:";
> +
> + return strstarts(namespace, prefix) &&
> + !strcmp(namespace + strlen(prefix), modname);
> +}
> +
> static void check_exports(struct module *mod)
> {
> struct symbol *s, *exp;
> @@ -1709,7 +1717,8 @@ static void check_exports(struct module
>
> basename = get_basename(mod->name);
>
> - if (!contains_namespace(&mod->imported_namespaces,
> exp->namespace)) {
> + if (!verify_module_namespace(exp->namespace, basename) &&
> + !contains_namespace(&mod->imported_namespaces,
> exp->namespace)) {
> modpost_log(!allow_missing_ns_imports,
> "module %s uses symbol %s from namespace
> %s, but does not import it.\n",
> basename, exp->name, exp->namespace);
>
>
--
Best Regards
Masahiro Yamada
