From: Maxim Levitsky mlevitsk@redhat.com
commit ad8f9e69942c7db90758d9d774157e53bce94840 upstream.
Update the emulation mode when handling writes to CR0, because toggling CR0.PE switches between Real and Protected Mode, and toggling CR0.PG when EFER.LME=1 switches between Long and Protected Mode.
This is likely a benign bug because there is no writeback of state, other than the RIP increment, and when toggling CR0.PE, the CPU has to execute code from a very low memory address.
Signed-off-by: Maxim Levitsky mlevitsk@redhat.com Message-Id: 20221025124741.228045-14-mlevitsk@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/emulate.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3639,11 +3639,25 @@ static int em_movbe(struct x86_emulate_c
static int em_cr_write(struct x86_emulate_ctxt *ctxt) { - if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val)) + int cr_num = ctxt->modrm_reg; + int r; + + if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val)) return emulate_gp(ctxt, 0);
/* Disable writeback. */ ctxt->dst.type = OP_NONE; + + if (cr_num == 0) { + /* + * CR0 write might have updated CR0.PE and/or CR0.PG + * which can affect the cpu's execution mode. + */ + r = emulator_recalc_and_set_mode(ctxt); + if (r != X86EMUL_CONTINUE) + return r; + } + return X86EMUL_CONTINUE; }