livepatch: Validate module/old func name length

livepatch module author can pass module name/old function name with more
than the defined character limit. With obj->name length greater than
MODULE_NAME_LEN, the livepatch module gets loaded but waits forever on
the module specified by obj->name to be loaded. It also populates a /sys
directory with an untruncated object name.

In the case of funcs->old_name length greater then KSYM_NAME_LEN, it
would not match against any of the symbol table entries. Instead loop
through the symbol table comparing them against a nonexisting function,
which can be avoided.

The same issues apply, to misspelled/incorrect names. At least gatekeep
the modules with over the limit string length, by checking for their
length during livepatch module registration.

Cc: stable@vger.kernel.org
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

kernel/livepatch/core.c

@@ -678,6 +678,9 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 	if (!func->old_name || !func->new_func)
 		return -EINVAL;
 
+	if (strlen(func->old_name) >= KSYM_NAME_LEN)
+		return -EINVAL;
+
 	INIT_LIST_HEAD(&func->stack_node);
 	func->patched = false;
 	func->transition = false;
@@ -751,6 +754,9 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 	if (!obj->funcs)
 		return -EINVAL;
 
+	if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
+		return -EINVAL;
+
 	obj->patched = false;
 	obj->mod = NULL;