AZL-47642

In the Linux kernel, the following vulnerability has been resolved:

kprobes: Fix possible use-after-free issue on kprobe registration

When unloading a module, its state is changing MODULESTATELIVE -> MODULESTATEGOING -> MODULESTATEUNFORMED. Each change will take a time. is_module_text_address() and __module_text_address() works with MODULESTATELIVE and MODULESTATEGOING. If we use is_module_text_address() and __module_text_address() separately, there is a chance that the first one is succeeded but the next one is failed because module->state becomes MODULESTATEUNFORMED between those operations.

In check_kprobe_address_safe(), if the second __module_text_address() is failed, that is ignored because it expected a kerneltext address. But it may have failed simply because module->state has been changed to MODULESTATEUNFORMED. In this case, armkprobe() will try to modify non-exist module text address (use-after-free).

To fix this problem, we should not use separated is_module_text_address() and __module_text_address(), but use only __module_text_address() once and do try_module_get(module) which is only available with MODULESTATELIVE.