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

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;