On Thu, May 26, 2022 at 09:08:15PM +0000, Sean Christopherson wrote: > Bug the VM, i.e. kill it, if the emulator accesses a non-existent GPR, > i.e. generates an out-of-bounds GPR index. Continuing on all but > gaurantees some form of data corruption in the guest, e.g. even if KVM > were to redirect to a dummy register, KVM would be incorrectly read zeros > and drop writes. > > Note, bugging the VM doesn't completely prevent data corruption, e.g. the > current round of emulation will complete before the vCPU bails out to > userspace. But, the very act of killing the guest can also cause data > corruption, e.g. due to lack of file writeback before termination, so > taking on additional complexity to cleanly bail out of the emulator isn't > justified, the goal is purely to stem the bleeding and alert userspace > that something has gone horribly wrong, i.e. to avoid _silent_ data > corruption. > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> I like this -- this ends up failing in a relatively clean fashion. (i.e. it's not actually a BUG(), but rather tells the VM to stop.) Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
