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authorNadav Amit <namit@cs.technion.ac.il>2014-10-28 00:03:43 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2014-11-02 07:54:55 +0100
commit7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2 (patch)
tree5c374dad5036d05134f833c10073bc89a0f85657 /arch
parentfd56e1546a5f734290cbedd2b81c518850736511 (diff)
downloadlinux-sh-7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2.tar.gz
KVM: x86: Fix far-jump to non-canonical check
Commit d1442d85cc30 ("KVM: x86: Handle errors when RIP is set during far jumps") introduced a bug that caused the fix to be incomplete. Due to incorrect evaluation, far jump to segment with L bit cleared (i.e., 32-bit segment) and RIP with any of the high bits set (i.e, RIP[63:32] != 0) set may not trigger #GP. As we know, this imposes a security problem. In addition, the condition for two warnings was incorrect. Fixes: d1442d85cc30ea75f7d399474ca738e0bc96f715 Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il> [Add #ifdef CONFIG_X86_64 to avoid complaints of undefined behavior. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/emulate.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 52a96270b560..5edf088ca51e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -574,12 +574,14 @@ static inline int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst,
case 4:
ctxt->_eip = (u32)dst;
break;
+#ifdef CONFIG_X86_64
case 8:
if ((cs_l && is_noncanonical_address(dst)) ||
- (!cs_l && (dst & ~(u32)-1)))
+ (!cs_l && (dst >> 32) != 0))
return emulate_gp(ctxt, 0);
ctxt->_eip = dst;
break;
+#endif
default:
WARN(1, "unsupported eip assignment size\n");
}
@@ -2035,7 +2037,7 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt)
rc = assign_eip_far(ctxt, ctxt->src.val, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
- WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
+ WARN_ON(ctxt->mode != X86EMUL_MODE_PROT64);
/* assigning eip failed; restore the old cs */
ops->set_segment(ctxt, old_sel, &old_desc, 0, VCPU_SREG_CS);
return rc;
@@ -2132,7 +2134,7 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt)
return rc;
rc = assign_eip_far(ctxt, eip, new_desc.l);
if (rc != X86EMUL_CONTINUE) {
- WARN_ON(!ctxt->mode != X86EMUL_MODE_PROT64);
+ WARN_ON(ctxt->mode != X86EMUL_MODE_PROT64);
ops->set_segment(ctxt, old_cs, &old_desc, 0, VCPU_SREG_CS);
}
return rc;