Submission access is checked only when viewing a webform node, but it is not validated when submitting the form itself. This can cause that a form can be submitted, if the user isn't allowed to submit it (e.g was logged out in an other window / another user logged in without submit permission).
Test case: Limit Submission access to authenticated users only, authenticate to view form, log out in an other browser window, submit the form
Desired behavior: validate submission access like validating e.g. per user submission limit
Actual behavior: the form can be submitted without any error message
Attached a patch that possibly fix this behavior.