Long latency MMIO mapping operations are not preemptible [XSA-125, CVE-2015-2752] Unmediated PCI command register access in qemu [XSA-126, CVE-2015-2756] Certain domctl operations may be abused to lock up the host [XSA-127, CVE-2015-2751] update to xen-4.3.4

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.

Xen was updated 4.4.2_01 to address three security issues and functional bugs.

The following vulnerabilities were fixed :

  - Long latency MMIO mapping operations are not preemptible     (XSA-125, CVE-2015-2752, bnc#922705)

  - Unmediated PCI command register access in qemu (XSA-126,     CVE-2015-2756, bnc#922706)

  - Certain domctl operations may be abused to lock up the     host (XSA-127, CVE-2015-2751, bnc#922709)

The update package also includes non-security fixes. See advisory for details.

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

The Xen Project reports :

XSA-77 put the majority of the domctl operations on a list excepting them from having security advisories issued for them if any effects their use might have could hamper security. Subsequently some of them got declared disaggregation safe, but for a small subset this was not really correct: Their (mis-)use may result in host lockups.

As a result, the potential security benefits of toolstack disaggregation are not always fully realised.

Domains deliberately given partial management control may be able to deny service to the entire host.

As a result, in a system designed to enhance security by radically disaggregating the management, the security may be reduced. But, the security will be no worse than a non-disaggregated design.

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

  - fdc: force the fifo access to be in bounds of the     allocated buffer During processing of certain commands     such as FD_CMD_READ_ID and     FD_CMD_DRIVE_SPECIFICATION_COMMAND the fifo memory     access could get out of bounds leading to memory     corruption with values coming from the guest. Fix this     by making sure that the index is always bounded by the     allocated memory. This is CVE-2015-3456.

    XSA-133 (CVE-2015-3456)

  - fdc: force the fifo access to be in bounds of the     allocated buffer During processing of certain commands     such as FD_CMD_READ_ID and     FD_CMD_DRIVE_SPECIFICATION_COMMAND the fifo memory     access could get out of bounds leading to memory     corruption with values coming from the guest. Fix this     by making sure that the index is always bounded by the     allocated memory. This is CVE-2015-3456.

    XSA-133 (CVE-2015-3456)

  - domctl: don't allow a toolstack domain to call     domain_pause on itself These DOMCTL subops were     accidentally declared safe for disaggregation in the     wake of XSA-77. This is XSA-127. (CVE-2015-2751)

  - xen: limit guest control of PCI command register     Otherwise the guest can abuse that control to cause e.g.
    PCIe Unsupported Request responses (by disabling memory     and/or I/O decoding and subsequently causing [CPU side]     accesses to the respective address ranges), which     (depending on system configuration) may be fatal to the     host. This is CVE-2015-2756 / XSA-126.

    Conflicts:
    tools/qemu-xen-traditional-dir/hw/pass-through.c     (CVE-2015-2756)

  - xen: limit guest control of PCI command register     Otherwise the guest can abuse that control to cause e.g.
    PCIe Unsupported Request responses (by disabling memory     and/or I/O decoding and subsequently causing [CPU side]     accesses to the respective address ranges), which     (depending on system configuration) may be fatal to the     host. This is CVE-2015-2756 / XSA-126. (CVE-2015-2756)

  - Limit XEN_DOMCTL_memory_mapping hypercall to only     process up to 64 GFNs (or less) Said hypercall for large     BARs can take quite a while. As such we can require that     the hypercall MUST break up the request in smaller     values. Another approach is to add preemption to it -     whether we do the preemption using     hypercall_create_continuation or returning EAGAIN to     userspace (and have it re-invocate the call) - either     way the issue we cannot easily solve is that in     'map_mmio_regions' if we encounter an error we MUST call     'unmap_mmio_regions' for the whole BAR region. Since the     preemption would re-use input fields such as nr_mfns,     first_gfn, first_mfn - we would lose the original values
    - and only undo what was done in the current round (i.e.
    ignoring anything that was done prior to earlier     preemptions). Unless we re-used the return value as     'EAGAIN|nr_mfns_done<<10' but that puts a limit (since     the return value is a long) on the amount of nr_mfns     that can provided. This patch sidesteps this problem by :

  - Setting an hard limit of nr_mfns having to be 64 or     less.

  - Toolstack adjusts correspondingly to the nr_mfn limit.

  - If the there is an error when adding the toolstack will     call the remove operation to remove the whole region.
    The need to break this hypercall down is for large BARs     can take more than the guest (initial domain usually)     time-slice. This has the negative result in that the     guest is locked out for a long duration and is unable to     act on any pending events. We also augment the code to     return zero if nr_mfns instead of trying to the     hypercall. Suggested-by: Jan Beulich 

    This is CVE-2015-2752 / XSA-125. (CVE-2015-2752)

XEN was updated to fix two security issues and bugs.

Security issues fixed :

  - CVE-2015-3340: Xen did not initialize certain fields,     which allowed certain remote service domains to obtain     sensitive information from memory via a (1)     XEN_DOMCTL_gettscinfo or (2)     XEN_SYSCTL_getdomaininfolist request.

  - CVE-2015-2751: Xen, when using toolstack disaggregation,     allowed remote domains with partial management control     to cause a denial of service (host lock) via unspecified     domctl operations.

  - CVE-2015-2752: The XEN_DOMCTL_memory_mapping hypercall     in Xen, when using a PCI passthrough device, was not     preemptable, which allowed local x86 HVM domain users to     cause a denial of service (host CPU consumption) via a     crafted request to the device model (qemu-dm).

  - CVE-2015-3456: Fixed a buffer overflow in the floppy     drive emulation, which could be used to denial of     service attacks or potential code execution against the     host.

Bugs fixed :

  - xentop: Fix memory leak on read failure

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

xen was updated to fix the following security issues :

  - CVE-2015-5165: QEMU leak of uninitialized heap memory in     rtl8139 device model (bsc#939712, XSA-140)

  - CVE-2015-5166: Use after free in QEMU/Xen block unplug     protocol (bsc#939709, XSA-139)

  - CVE-2015-2751: Certain domctl operations could have be     used to lock up the host (bsc#922709, XSA-127)

  - CVE-2015-3259: xl command line config handling stack     overflow (bsc#935634, XSA-137)

  - CVE-2015-4164: DoS through iret hypercall handler     (bsc#932996, XSA-136)

  - CVE-2015-5154: Host code execution via IDE subsystem     CD-ROM (bsc#938344)

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

ID	名称	产品	系列	发布时间	最近更新时间	严重程度
82730	Fedora 20 : xen-4.3.4-2.fc20 (2015-5402)	Nessus	Fedora Local Security Checks	2015/4/13	2021/1/11	high
83714	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2015:0701-1)	Nessus	SuSE Local Security Checks	2015/5/20	2021/1/6	high
84694	FreeBSD : xen-kernel -- Certain domctl operations may be abused to lock up the host (103a47d5-27e7-11e5-a4a5-002590263bf5)	Nessus	FreeBSD Local Security Checks	2015/7/14	2021/1/6	high
83482	OracleVM 3.3 : xen (OVMSA-2015-0057) (Venom)	Nessus	OracleVM Local Security Checks	2015/5/15	2021/1/4	high
83757	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2015:0923-1) (Venom)	Nessus	SuSE Local Security Checks	2015/5/21	2023/9/28	high
85791	SUSE SLED11 / SLES11 Security Update : xen (SUSE-SU-2015:1479-1)	Nessus	SuSE Local Security Checks	2015/9/4	2021/1/6	high

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