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 MODULE_STATE_LIVE ->
MODULE_STATE_GOING -> MODULE_STATE_UNFORMED. Each change will take
a time. is_module_text_address() and __module_text_address()
works with MODULE_STATE_LIVE and MODULE_STATE_GOING.
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 MODULE_STATE_UNFORMED
between those operations.
In check_kprobe_address_safe(), if the second __module_text_address()
is failed, that is ignored because it expected a kernel_text address.
But it may have failed simply because module->state has been changed
to MODULE_STATE_UNFORMED. In this case, arm_kprobe() 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
MODULE_STATE_LIVE.