On 2017/9/6 20:30, Vladimir Murzin wrote: > On 06/09/17 13:14, gengdongjiu wrote: >> >> >> On 2017/9/6 20:00, Vladimir Murzin wrote: >>> On 06/09/17 11:35, gengdongjiu wrote: >>>> Vladimir, >>>> >>>> On 2017/9/6 17:41, Vladimir Murzin wrote: >>>>> Can you please elaborate on cases where PAN is not enabled? >>>> >>>> I mean the informal private usage, For example, he disabled the PAN dynamically to let kernel space to access the user space. >>>> After he dynamic disabled the PAN, then switched to guest OS. after return to host. he found the PAN stage is modified. >>>> Of cause this is not a formal usage, in our host kernel, it is always enabled, no dynamic change, but I means it may exist such cases. >>>> >>>> >>> >>> So, in short, there is no real issue with PAN, right? What about UAO? >> For the PAN, if host OS dynamically enable/disable PAN should have issue. >> Do you think that is not a issue as above description? >> >> "host OS dynamically disable the PAN, but after go back from the guest OS, The PAN is unexpectedly enabled" > > Do you see effect of "PAN is unexpectedly enabled"? In fact I did not encounter this case, but I think it can exist. I think if host OS dynamically disable PAN, it wants the host kernel access the user space address space not through copy_to/from_user API. Now if it is unexpectedly enabled, when host kernel still accesses the user space address, it will happen MMU fault exception. > > Cheers > Vladimir > >> >>> >>> Cheers >>> Vladimir >>> >>> . >>> >> >> > > > . >
