Off-by-one error in the flask_security_avc_cachestats function in xsm/flask/flask_op.c in Xen 4.2.x and 4.3.x, when the maximum number of physical CPUs are in use, allows local users to cause a denial of service (host crash) or obtain sensitive information from hypervisor memory by leveraging a FLASK_AVC_CACHESTAT hypercall, which triggers a buffer over-read.

The remote host is affected by the vulnerability described in GLSA-201407-03 (Xen: Multiple Vunlerabilities)

    Multiple vulnerabilities have been discovered in Xen. Please review the       CVE identifiers referenced below for details.
  Impact :

    A remote attacker can utilize multiple vectors to execute arbitrary       code, cause Denial of Service, or gain access to data on the host.
  Workaround :

    There is no known workaround at this time.

Xen was updated to fix various bugs and security issues :

Update to Xen version 4.2.4 c/s 26280.

  - bnc#861256 - CVE-2014-1950: xen: XSA-88: use-after-free     in xc_cpupool_getinfo() under memory pressure. (fix     included with update)

  - bnc#863297: xend/pvscsi: recognize also SCSI CDROM     devices

  - bnc#858496 - CVE-2014-1642: Xen: XSA-83: Out-of-memory     condition yielding memory corruption during IRQ setup

  - bnc#860163 - xen: XSA-84: integer overflow in several     XSM/Flask hypercalls (CVE-2014-1891 CVE-2014-1892     CVE-2014-1893 CVE-2014-1894)

  - bnc#860165 - CVE-2014-1895: xen: XSA-85: Off-by-one     error in FLASK_AVC_CACHESTAT hypercall

  - bnc#860300 - CVE-2014-1896: xen: XSA-86: libvchan     failure handling malicious ring indexes

  - bnc#860302 - CVE-2014-1666: xen: XSA-87:
    PHYSDEVOP_(prepare,release)_msix exposed to unprivileged     guests

  - bnc#858311 - Server is not booting in kernel XEN after     latest updates - (XEN) setup 0000:00:18.0 for d0 failed     (-19)

  - bnc#858496 - CVE-2014-1642: Xen: XSA-83: Out-of-memory     condition yielding memory corruption during IRQ setup

  - bnc#853049 - CVE-2013-6885: xen: XSA-82: Guest     triggerable AMD CPU erratum may cause host hang

  - bnc#853048 - CVE-2013-6400: xen: XSA-80: IOMMU TLB     flushing may be inadvertently suppressed

  - bnc#831120 - CVE-2013-2212: xen: XSA-60: Excessive time     to disable caching with HVM guests with PCI passthrough

  - bnc#848014 - [HP HPS] Xen hypervisor panics on 8-blades     nPar with 46-bit memory addressing

  - bnc#833251 - [HP BCS SLES11 Bug]: In HPs UEFI x86_64     platform and with xen environment, in booting stage ,xen     hypervisor will panic.

  - pygrub: Support (/dev/xvda) style disk specifications

  - bnc#849667 - CVE-2014-1895: xen: XSA-74: Lock order     reversal between page_alloc_lock and mm_rwlock

  - bnc#849668 - CVE-2013-4554: xen: XSA-76: Hypercalls     exposed to privilege rings 1 and 2 of HVM guests

  - bnc#842417 - In HPs UEFI x86_64 platform and sles11sp3     with xen environment, dom0 will soft lockup on multiple     blades nPar.

  - bnc#848014 - [HP HPS] Xen hypervisor panics on 8-blades     nPar with 46-bit memory addressing

  - bnc#846849 - Soft lockup with PCI passthrough and many     VCPUs

  - bnc#833483 - Boot Failure with xen kernel in UEFI mode     with error 'No memory for trampoline'

  - bnc#849665 - CVE-2013-4551: xen: XSA-75: Host crash due     to guest VMX instruction execution

  - The upstream version of checking for xend when using the     'xl' command is used is not working.

  - bnc#840997 - It is possible to start a VM twice on the     same node.

  - bnc#848657 - xen: CVE-2013-4494: XSA-73: Lock order     reversal between page allocation and grant table locks

The SUSE Linux Enterprise Server 11 Service Pack 3 Xen hypervisor and toolset has been updated to 4.2.4 to fix various bugs and security issues :

The following security issues have been addressed :

  - XSA-60: CVE-2013-2212: The vmx_set_uc_mode function in     Xen 3.3 through 4.3, when disabling chaches, allows     local HVM guests with access to memory mapped I/O     regions to cause a denial of service (CPU consumption     and possibly hypervisor or guest kernel panic) via a     crafted GFN range. (bnc#831120)

  - XSA-80: CVE-2013-6400: Xen 4.2.x and 4.3.x, when using     Intel VT-d and a PCI device has been assigned, does not     clear the flag that suppresses IOMMU TLB flushes when     unspecified errors occur, which causes the TLB entries     to not be flushed and allows local guest administrators     to cause a denial of service (host crash) or gain     privileges via unspecified vectors. (bnc#853048)

  - XSA-82: CVE-2013-6885: The microcode on AMD 16h 00h     through 0Fh processors does not properly handle the     interaction between locked instructions and     write-combined memory types, which allows local users to     cause a denial of service (system hang) via a crafted     application, aka the errata 793 issue. (bnc#853049)

  - XSA-83: CVE-2014-1642: The IRQ setup in Xen 4.2.x and     4.3.x, when using device passthrough and configured to     support a large number of CPUs, frees certain memory     that may still be intended for use, which allows local     guest administrators to cause a denial of service     (memory corruption and hypervisor crash) and possibly     execute arbitrary code via vectors related to an     out-of-memory error that triggers a (1) use-after-free     or (2) double free. (bnc#860092)

  - XSA-84: CVE-2014-1891: The FLASK_{GET,SET}BOOL,     FLASK_USER and FLASK_CONTEXT_TO_SID suboperations of the     flask hypercall are vulnerable to an integer overflow on     the input size. The hypercalls attempt to allocate a     buffer which is 1 larger than this size and is therefore     vulnerable to integer overflow and an attempt to     allocate then access a zero byte buffer. (bnc#860163)

  - XSA-84: CVE-2014-1892 / CVE-2014-1893: Xen 3.3 through     4.1, while not affected by the above overflow, have a     different overflow issue on FLASK_{GET,SET}BOOL and     expose unreasonably large memory allocation to     aribitrary guests. (bnc#860163)

  - XSA-84: CVE-2014-1894: Xen 3.2 (and presumably earlier)     exhibit both problems with the overflow issue being     present for more than just the suboperations listed     above. (bnc#860163)

  - XSA-85: CVE-2014-1895: The FLASK_AVC_CACHESTAT     hypercall, which provides access to per-cpu statistics     on the Flask security policy, incorrectly validates the     CPU for which statistics are being requested.
    (bnc#860165)

  - XSA-86: CVE-2014-1896: libvchan (a library for     inter-domain communication) does not correctly handle     unusual or malicious contents in the xenstore ring. A     malicious guest can exploit this to cause a     libvchan-using facility to read or write past the end of     the ring. (bnc#860300)

  - XSA-87: CVE-2014-1666: The do_physdev_op function in Xen     4.1.5, 4.1.6.1, 4.2.2 through 4.2.3, and 4.3.x does not     properly restrict access to the (1)     PHYSDEVOP_prepare_msix and (2) PHYSDEVOP_release_msix     operations, which allows local PV guests to cause a     denial of service (host or guest malfunction) or     possibly gain privileges via unspecified vectors.
    (bnc#860302)

  - XSA-88: CVE-2014-1950: Use-after-free vulnerability in     the xc_cpupool_getinfo function in Xen 4.1.x through     4.3.x, when using a multithreaded toolstack, does not     properly handle a failure by the xc_cpumap_alloc     function, which allows local users with access to     management functions to cause a denial of service (heap     corruption) and possibly gain privileges via unspecified     vectors. (bnc#861256)

Also the following non-security bugs have been fixed :

  - Fixed boot problems with Xen kernel. '(XEN) setup     0000:00:18.0 for d0 failed (-19)'. (bnc#858311)

  - Fixed Xen hypervisor panic on 8-blades nPar with 46-bit     memory addressing. (bnc#848014)

  - Fixed Xen hypervisor panic in HP's UEFI x86_64 platform     and with xen environment, in booting stage. (bnc#833251)

  - xend/pvscsi: recognize also SCSI CDROM devices.
    (bnc#863297)

  - pygrub: Support (/dev/xvda) style disk specifications

three security fixes: integer overflow in several XSM/Flask hypercalls [XSA-84] Off-by-one error in FLASK_AVC_CACHESTAT hypercall [XSA-85] libvchan failure handling malicious ring indexes [XSA-86]

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

three security fixes: integer overflow in several XSM/Flask hypercalls [XSA-84], Off-by-one error in FLASK_AVC_CACHESTAT hypercall [XSA-85], libvchan failure handling malicious ring indexes [XSA-86]

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Type	Severity
76544	GLSA-201407-03 : Xen: Multiple Vunlerabilities	Nessus	Gentoo Local Security Checks	Local	high
75312	openSUSE Security Update : xen (openSUSE-SU-2014:0483-1)	Nessus	SuSE Local Security Checks	Local	high
73015	SuSE 11.3 Security Update : Xen (SAT Patch Number 8973)	Nessus	SuSE Local Security Checks	Local	high
72540	Fedora 19 : xen-4.2.3-15.fc19 (2014-2188)	Nessus	Fedora Local Security Checks	Local	medium
72539	Fedora 20 : xen-4.3.1-9.fc20 (2014-2170)	Nessus	Fedora Local Security Checks	Local	medium

Detections

Analytics

CVE-2014-1895

high

Tenable Plugins

high

high

high

medium

medium