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.