On Fri, Jul 20, 2018 at 4:49 PM, Jessica Yu <jeyu@xxxxxxxxxx> wrote:
Thanks. Also, it looks like we're currently just warning (in both
modpost and on module load) if a module uses symbols from a namespace
it doesn't import. Are you also planning to eventually introduce
namespace enforcement?
This is something I've definitely been thinking about, and was curious
what others would think. My main concern with enforcement is that it
will start failing to load out-of-tree modules that use newly
namespaced symbols. On the other hand, I think those modules will need
to be rebuilt anyway to be able to load, because the changes to struct
kernel_symbol make them incompatible with the current kernel. That
could be another reason for having these symbols in a special section
(with its own struct namespaced_kernel_symbol); but on the other hand,
it would make the module loader more complex just to facilitate
out-of-tree drivers, and I'm not sure where the trade-off between
those two falls.
It'd be trivial to fail the module build in
modpost as well as reject the module on load if it uses an exported
symbol belonging to a namespace it doesn't import. Although, I'd go
with the warnings for a development cycle or two, to gently introduce
the change in API and let other subsystems as well as out-of-tree
module developers catch up.
An approach like that makes sense to me. Another alternative would be
to make it a CONFIG_ option, and let distros/etc. decide what they are
comfortable with.
Thanks,
Martijn
Jessica
Also, this would get rid of the extra __knsimport section, the extra
ns_dependencies field in struct module, and all those helper functions
that
manage it. In addition, having the modinfo tag may potentially help with
debugging as we have the namespace imports clearly listed if we don't
have
the source code for a module. We'd probably need to modify get_modinfo()
to
handle multiple import: tags though. Luis [1] had written some code a
while
ago to handle multiple (of the same) modinfo tags.
Thoughts on this?
Thanks,
Jessica
[1] https://lkml.kernel.org/r/20171130023605.29568-3-mcgrof@xxxxxxxxxx
getname:
/* We must make copy under the lock if we failed to get ref. */
strncpy(ownername, module_name(owner), MODULE_NAME_LEN);
@@ -3061,6 +3118,11 @@ static int find_module_sections(struct module
*mod,
struct load_info *info)
sizeof(*mod->gpl_syms),
&mod->num_gpl_syms);
mod->gpl_crcs = section_addr(info, "__kcrctab_gpl");
+
+ mod->ns_imports = section_objs(info, "__knsimport",
+ sizeof(*mod->ns_imports),
+ &mod->num_ns_imports);
+
mod->gpl_future_syms = section_objs(info,
"__ksymtab_gpl_future",
sizeof(*mod->gpl_future_syms),
@@ -3381,6 +3443,19 @@ static int post_relocation(struct module *mod,
const struct load_info *info)
return module_finalize(info->hdr, info->sechdrs, mod);
}
+static void verify_namespace_dependencies(struct module *mod)
+{
+ struct module_ns_dep *ns_dep;
+
+ list_for_each_entry(ns_dep, &mod->ns_dependencies, ns_dep) {
+ if (!module_imports_ns(mod, ns_dep->namespace)) {
+ pr_warn("%s: module uses symbols from namespace
%s,"
+ " but does not import it.\n",
+ mod->name, ns_dep->namespace);
+ }
+ }
+}
+
/* Is this module of this name done loading? No locks held. */
static bool finished_loading(const char *name)
{
@@ -3682,6 +3757,8 @@ static int load_module(struct load_info *info,
const
char __user *uargs,
if (err)
goto free_module;
+ INIT_LIST_HEAD(&mod->ns_dependencies);
+
#ifdef CONFIG_MODULE_SIG
mod->sig_ok = info->sig_ok;
if (!mod->sig_ok) {
@@ -3730,6 +3807,8 @@ static int load_module(struct load_info *info,
const
char __user *uargs,
if (err < 0)
goto free_modinfo;
+ verify_namespace_dependencies(mod);
+
flush_module_icache(mod);
/* Now copy in args */
--
2.18.0.203.gfac676dfb9-goog
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