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KVM: x86: Emulation of call may use incorrect stack size

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On long-mode, when far call that changes cs.l takes place, the stack size is
determined by the new mode.  For instance, if we go from 32-bit mode to 64-bit
mode, the stack-size if 64.  KVM uses the old stack size.

Fix it.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2015-01-26 09:32:27 +02:00 committed by Paolo Bonzini
parent bac155310b
commit 82268083fa
1 changed files with 18 additions and 7 deletions
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25
arch/x86/kvm/emulate.c
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@ -741,19 +741,26 @@ static int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst,
const struct desc_struct *cs_desc)
{
enum x86emul_mode mode = ctxt->mode;
int rc;
#ifdef CONFIG_X86_64
if (ctxt->mode >= X86EMUL_MODE_PROT32 && cs_desc->l) {
u64 efer = 0;
if (ctxt->mode >= X86EMUL_MODE_PROT16) {
if (cs_desc->l) {
u64 efer = 0;
ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
if (efer & EFER_LMA)
mode = X86EMUL_MODE_PROT64;
ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
if (efer & EFER_LMA)
mode = X86EMUL_MODE_PROT64;
} else
mode = X86EMUL_MODE_PROT32; /* temporary value */
}
#endif
if (mode == X86EMUL_MODE_PROT16 || mode == X86EMUL_MODE_PROT32)
mode = cs_desc->d ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
return assign_eip(ctxt, dst, mode);
rc = assign_eip(ctxt, dst, mode);
if (rc == X86EMUL_CONTINUE)
ctxt->mode = mode;
return rc;
}
static inline int jmp_rel(struct x86_emulate_ctxt *ctxt, int rel)
@ -3062,6 +3069,7 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
struct desc_struct old_desc, new_desc;
const struct x86_emulate_ops *ops = ctxt->ops;
int cpl = ctxt->ops->cpl(ctxt);
enum x86emul_mode prev_mode = ctxt->mode;
old_eip = ctxt->_eip;
ops->get_segment(ctxt, &old_cs, &old_desc, NULL, VCPU_SREG_CS);
@ -3085,11 +3093,14 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
rc = em_push(ctxt);
/* If we failed, we tainted the memory, but the very least we should
restore cs */
if (rc != X86EMUL_CONTINUE)
if (rc != X86EMUL_CONTINUE) {
pr_warn_once("faulting far call emulation tainted memory\n");
goto fail;
}
return rc;
fail:
ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS);
ctxt->mode = prev_mode;
return rc;
}