livepatch: Validate module/old func name length

kamalesh-babulal · Jiri Kosina · commit 6e9df95b76ca · 2018-07-23T12:12:00.000+02:00
livepatch module author can pass module name/old function name with more
than the defined character limit. With obj-&gt;name length greater than
MODULE_NAME_LEN, the livepatch module gets loaded but waits forever on
the module specified by obj-&gt;name to be loaded. It also populates a /sys
directory with an untruncated object name.

In the case of funcs-&gt;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 &lt;kamalesh@linux.vnet.ibm.com&gt;
Acked-by: Josh Poimboeuf &lt;jpoimboe@redhat.com&gt;
Signed-off-by: Jiri Kosina &lt;jkosina@suse.cz&gt;
diff --git a/kernel/livepatch/core.c b/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;
 
