On 1/14/22 16:19, Mark Rutland wrote:
I also think there is another issue here. When an IRQ is taken from SIE, will user_mode(regs) always be false, or could it be true if the guest userspace is running? If it can be true I think tha context tracking checks can complain, and it*might* be possible to trigger a panic().
I think that it would be false, because the guest PSW is in the SIE block and switched on SIE entry and exit, but I might be incorrect.
Paolo
In irqentry_enter(), if user_mode(regs) == true, we call irqentry_enter_from_user_mode -> __enter_from_user_mode(). There we check that the context is CONTEXT_USER, but IIUC that will be CONTEXT_GUEST at this point. We also call arch_check_user_regs(), and IIUC this might permit a malicious guest to trigger a host panic by way of debug_user_asce(), but I may have misunderstood and that might not be possible.
