KVM: x86/emulator: Fix handing of POP SS to correctly set interruptibility

commit b2d95217c793f3c6068dd8f96f79208de33e9732 upstream.

The emulator checks the wrong variable while setting the CPU
interruptibility state, the target segment is embedded in the instruction
opcode, not the ModR/M register.  Fix the condition.

Signed-off-by: Michal Luczaj <mhal@rbox.co>
Fixes: b40da73bbcf1 ("KVM: emulate: POP SS triggers a MOV SS shadow too")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20220821215900.1419215-1-mhal@rbox.co
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index fcb59dc54bf562ab835a1bbd803e1977c28a4201..1a1c9c9f3a31f4a83a268c763fb2e1b5d15fa7a7 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2020,7 +2020,7 @@ static int em_pop_sreg(struct x86_emulate_ctxt *ctxt)
        if (rc != X86EMUL_CONTINUE)
                return rc;
 
-       if (ctxt->modrm_reg == VCPU_SREG_SS)
+       if (seg == VCPU_SREG_SS)
                ctxt->interruptibility = KVM_X86_SHADOW_INT_MOV_SS;
        if (ctxt->op_bytes > 2)
                rsp_increment(ctxt, ctxt->op_bytes - 2);