tree 8b5e04a3ff18733f18b68a7157e1884ab9eec0b9
parent 958e8e14fd24c0aa1fe6a6beb2b985cb638577d6
author Marc Zyngier <maz@kernel.org> 1588155715 +0100
committer Marc Zyngier <maz@kernel.org> 1588323068 +0100

KVM: arm64: Fix 32bit PC wrap-around

In the unlikely event that a 32bit vcpu traps into the hypervisor
on an instruction that is located right at the end of the 32bit
range, the emulation of that instruction is going to increment
PC past the 32bit range. This isn't great, as userspace can then
observe this value and get a bit confused.

Conversly, userspace can do things like (in the context of a 64bit
guest that is capable of 32bit EL0) setting PSTATE to AArch64-EL0,
set PC to a 64bit value, change PSTATE to AArch32-USR, and observe
that PC hasn't been truncated. More confusion.

Fix both by:
- truncating PC increments for 32bit guests
- sanitizing all 32bit regs every time a core reg is changed by
  userspace, and that PSTATE indicates a 32bit mode.

Cc: stable@vger.kernel.org
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>