OracleVM 3.2 : xen (OVMSA-2015-0063)

High Nessus Plugin ID 83966


The remote OracleVM host is missing one or more security updates.


The remote OracleVM system is missing necessary patches to address critical security updates :

- xen/pt: unknown PCI config space fields should be read-only ... by default. Add a per-device 'permissive' mode similar to pciback's to allow restoring previous behavior (and hence break security again, i.e. should be used only for trusted guests). This is part of XSA-131.

- xen/pt: add a few PCI config space field descriptions Since the next patch will turn all not explicitly described fields read-only by default, those fields that have guest writable bits need to be given explicit descriptors. This is a preparatory patch for XSA-131.

- xen/pt: mark reserved bits in PCI config space fields The adjustments are solely to make the subsequent patches work right (and hence make the patch set consistent), namely if permissive mode (introduced by the last patch) gets used (as both reserved registers and reserved fields must be similarly protected from guest access in default mode, but the guest should be allowed access to them in permissive mode). This is a preparatory patch for XSA-131. (CVE-2015-4106)

- xen/pt: mark all PCIe capability bits read-only xen_pt_emu_reg_pcie[]'s PCI_EXP_DEVCAP needs to cover all bits as read- only to avoid unintended write-back (just a precaution, the field ought to be read-only in hardware). This is a preparatory patch for XSA-131.

- xen/pt: split out calculation of throughable mask in PCI config space handling This is just to avoid having to adjust that calculation later in multiple places. Note that including ->ro_mask in get_throughable_mask's calculation is only an apparent (i.e. benign) behavioral change: For r/o fields it doesn't matter > whether they get passed through - either the same flag is also set in emu_mask (then there's no change at all) or the field is r/o in hardware (and hence a write won't change it anyway). This is a preparatory patch for XSA-131.

- xen/pt: correctly handle PM status bit xen_pt_pmcsr_reg_write needs an adjustment to deal with the RW1C nature of the not passed through bit 15 (PCI_PM_CTRL_PME_STATUS). This is a preparatory patch for XSA-131. (CVE-2015-4106)

- xen/pt: consolidate PM capability emu_mask There's no point in xen_pt_pmcsr_reg_[read,write] each ORing PCI_PM_CTRL_STATE_MASK and PCI_PM_CTRL_NO_SOFT_RESET into a local emu_mask variable - we can have the same effect by setting the field descriptor's emu_mask member suitably right away. Note that xen_pt_pmcsr_reg_write is being retained in order to allow later patches to be less intrusive. This is a preparatory patch for XSA-131.

- xen/MSI: don't open-code pass-through of enable bit modifications Without this the actual XSA-131 fix would cause the enable bit to not get set anymore (due to the write back getting suppressed there based on the OR of emu_mask, ro_mask, and res_mask). Note that the fiddling with the enable bit shouldn't really be done by qemu, but making this work right (via libxc and the hypervisor) will require more extensive changes, which can be postponed until after the security issue got addressed. This is a preparatory patch for XSA-131.

- xen/MSI-X: disable logging by default ... to avoid allowing the guest to cause the control domain's disk to fill. This is XSA-130. (CVE-2015-4105)

- xen: don't allow guest to control MSI mask register It's being used by the hypervisor. For now simply mimic a device not capable of masking, and fully emulate any accesses a guest may issue nevertheless as simple reads/writes without side effects. This is XSA-129.

- xen: properly gate host writes of modified PCI CFG contents The old logic didn't work as intended when an access spanned multiple fields (for example a 32-bit access to the location of the MSI Message Data field with the high 16 bits not being covered by any known field). Remove it and derive which fields not to write to from the accessed fields' emulation masks: When they're all ones, there's no point in doing any host write. This fixes a secondary issue at once: We obviously shouldn't make any host write attempt when already the host read failed. This is XSA-128.

Conflicts: tools/ioemu-remote/hw/pass-through.c (CVE-2015-4103)


Update the affected xen / xen-devel / xen-tools packages.

See Also

Plugin Details

Severity: High

ID: 83966

File Name: oraclevm_OVMSA-2015-0063.nasl

Version: $Revision: 2.6 $

Type: local

Published: 2015/06/03

Modified: 2017/02/14

Dependencies: 12634

Risk Information

Risk Factor: High


Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

Temporal Vector: CVSS2#E:U/RL:OF/RC:C

Vulnerability Information

CPE: p-cpe:/a:oracle:vm:xen, p-cpe:/a:oracle:vm:xen-devel, p-cpe:/a:oracle:vm:xen-tools, cpe:/o:oracle:vm_server:3.2

Required KB Items: Host/local_checks_enabled, Host/OracleVM/release, Host/OracleVM/rpm-list

Exploit Available: false

Exploit Ease: No known exploits are available

Patch Publication Date: 2015/06/02

Reference Information

CVE: CVE-2015-4103, CVE-2015-4104, CVE-2015-4105, CVE-2015-4106

BID: 74947, 74948, 74949, 74950

OSVDB: 122855, 122856, 122857, 122858