svn commit: r365775 - in head/sys/amd64/vmm: amd intel

[Ed Maste]

Author: emaste
Date: Tue Sep 15 21:04:27 2020
New Revision: 365775
URL: https://svnweb.freebsd.org/changeset/base/365775

Log:
  bhyve: do not permit write access to VMCB / VMCS
  
  Reported by:	Patrick Mooney
  Submitted by:	jhb
  Security:	CVE-2020-24718

Modified:
  head/sys/amd64/vmm/amd/svm.c
  head/sys/amd64/vmm/intel/vmx.c

Modified: head/sys/amd64/vmm/amd/svm.c
==============================================================================
--- head/sys/amd64/vmm/amd/svm.c	Tue Sep 15 21:00:25 2020	(r365774)
+++ head/sys/amd64/vmm/amd/svm.c	Tue Sep 15 21:04:27 2020	(r365775)
@@ -2227,8 +2227,11 @@ svm_setreg(void *arg, int vcpu, int ident, uint64_t va
 		return (svm_modify_intr_shadow(svm_sc, vcpu, val));
 	}
 
-	if (vmcb_write(svm_sc, vcpu, ident, val) == 0) {
-		return (0);
+	/* Do not permit user write access to VMCB fields by offset. */
+	if (!VMCB_ACCESS_OK(ident)) {
+		if (vmcb_write(svm_sc, vcpu, ident, val) == 0) {
+			return (0);
+		}
 	}
 
 	reg = swctx_regptr(svm_get_guest_regctx(svm_sc, vcpu), ident);

Modified: head/sys/amd64/vmm/intel/vmx.c
==============================================================================
--- head/sys/amd64/vmm/intel/vmx.c	Tue Sep 15 21:00:25 2020	(r365774)
+++ head/sys/amd64/vmm/intel/vmx.c	Tue Sep 15 21:04:27 2020	(r365775)
@@ -3341,6 +3341,10 @@ vmx_setreg(void *arg, int vcpu, int reg, uint64_t val)
 	if (vmxctx_setreg(&vmx->ctx[vcpu], reg, val) == 0)
 		return (0);
 
+	/* Do not permit user write access to VMCS fields by offset. */
+	if (reg < 0)
+		return (EINVAL);
+
 	error = vmcs_setreg(&vmx->vmcs[vcpu], running, reg, val);
 
 	if (error == 0) {