[POC 03/23] livepatch: Better checks of struct klp_object definition

Petr Mladek
2020-01-17T15:03:59Z

The number of user defined fields increased in struct klp_object after
spliting per-object livepatches. It was sometimes unclear why exactly
the module could not get loded when returned -EINVAL.

Add more checks for the split modules and write useful error
messages on particular errors.

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
kernel/livepatch/core.c | 91 ++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 82 insertions(+), 9 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index bb62c5407b75..ec7ffc7db3a7 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -756,9 +756,6 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
int ret;
const char *name;

- if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
- return -EINVAL;
-
obj->patched = false;

name = obj->name ? obj->name : "vmlinux";
@@ -851,8 +848,86 @@ static int klp_init_patch(struct klp_patch *patch)
return 0;
}

+static int klp_check_module_name(struct klp_object *obj, bool is_module)
+{
+ char mod_name[MODULE_NAME_LEN];
+ const char *expected_name;
+
+ if (is_module) {
+ snprintf(mod_name, sizeof(mod_name), "%s__%s",
+ obj->patch_name, obj->name);
+ expected_name = mod_name;
+ } else {
+ expected_name = obj->patch_name;
+ }
+
+ if (strcmp(expected_name, obj->mod->name)) {
+ pr_err("The module name %s does not match with obj->patch_name and obj->name. The expected name is: %s\n",
+ obj->mod->name, expected_name);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int klp_check_object(struct klp_object *obj, bool is_module)
+{
+
+ if (!obj->mod)
+ return -EINVAL;
+
+ if (!is_livepatch_module(obj->mod)) {
+ pr_err("module %s is not marked as a livepatch module\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+
+ if (!obj->patch_name) {
+ pr_err("module %s does not have set obj->patch_name\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+
+ if (strlen(obj->patch_name) >= MODULE_NAME_LEN) {
+ pr_err("module %s has too long obj->patch_name\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+
+ if (is_module) {
+ if (!obj->name) {
+ pr_err("module %s does not have set obj->name\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+ if (strlen(obj->name) >= MODULE_NAME_LEN) {
+ pr_err("module %s has too long obj->name\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+ } else if (obj->name) {
+ pr_err("module %s for vmlinux must not have set obj->name\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+
+ if (!obj->funcs) {
+ pr_err("module %s does not have set obj->funcs\n",
+ obj->mod->name);
+ return -EINVAL;
+ }
+
+ return klp_check_module_name(obj, is_module);
+}
+
int klp_add_object(struct klp_object *obj)
{
+ int ret;
+
+ ret = klp_check_object(obj, true);
+ if (ret)
+ return ret;
+
return 0;
}
EXPORT_SYMBOL_GPL(klp_add_object);
@@ -958,14 +1033,12 @@ int klp_enable_patch(struct klp_patch *patch)
{
int ret;

- if (!patch || !patch->obj || !patch->obj->mod)
+ if (!patch || !patch->obj)
return -EINVAL;

- if (!is_livepatch_module(patch->obj->mod)) {
- pr_err("module %s is not marked as a livepatch module\n",
- patch->obj->patch_name);
- return -EINVAL;
- }
+ ret = klp_check_object(patch->obj, false);
+ if (ret)
+ return ret;

if (!klp_initialized())
return -ENODEV;
--
2.16.4