On Wed, Sep 23, 2020 at 3:20 PM Yu, Yu-cheng <[email protected]> wrote: > > On 9/23/2020 3:08 PM, Dave Hansen wrote: > > On 9/23/20 3:06 PM, Yu, Yu-cheng wrote: > >> I think I'll add a check here for (r + 8) >= TASK_SIZE_MAX. It is > >> better than getting a fault. > > > > There's also wrmsr_safe(). > > > Yes, thanks. > > Since I am going to change this to: > > fpu__prepare_write(), then write to the XSAVES area. > > The kernel does not expect XRSTORS to fail ("Bad FPU state detected..." > message). So maybe still check the address first.
Surely there are plenty of ways to use ptrace() to poke garbage into the FPU state. We should be able to handle this type of failure somewhat gracefully.
