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Xen Security Advisory XSA-276
resource accounting issues in x86 IOREQ server handling
UPDATES IN VERSION 2
Allocation of pages used to communicate with external emulators did not
follow certain principles that are required for proper life cycle
management of guest exposed pages.
A compromised DM stubdomain may cause Xen to crash, resulting in a DoS
(Denial of Service) affecting the entire host. Privilege escalation
as well as information leaks cannot be ruled out.
Only Xen 4.11 is affected by this vulnerability. Xen 4.10 and older are
not affected by this vulnerability.
Only systems running HVM guests with their devicemodels in a
stubdomain are considered vulnerable. Note that attackers also need
to exploit the devicemodel in order to have access to this
Arm guests cannot leverage this vulnerability.
Running only PV guests will avoid this vulnerability.
(The security of a Xen system using stub domains is still better than
with a qemu-dm running as an unrestricted dom0 process. Therefore
users with these configurations should not switch to an unrestricted
This issue was discovered by Julien Grall of ARM.
Applying the appropriate set of attached patches resolves this issue.
xsa276-4.11/*.patch Xen 4.11.x
$ sha256sum xsa276* xsa276*/*
DEPLOYMENT DURING EMBARGO
Deployment of the patches and/or mitigations described above (or
others which are substantially similar) is permitted during the
embargo, even on public-facing systems with untrusted guest users and
But: Distribution of updated software is prohibited (except to other
members of the predisclosure list).
Predisclosure list members who wish to deploy significantly different
patches and/or mitigations, please contact the Xen Project Security
(Note: this during-embargo deployment notice is retained in
post-embargo publicly released Xen Project advisories, even though it
is then no longer applicable. This is to enable the community to have
oversight of the Xen Project Security Team's decisionmaking.)
For more information about permissible uses of embargoed information,
consult the Xen Project community's agreed Security Policy:
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Xen-users mailing list
xsa276.meta (812 bytes) Download Attachment
xsa276-4.11/0001-x86-hvm-ioreq-fix-page-referencing.patch (5K) Download Attachment
xsa276-4.11/0002-x86-hvm-ioreq-use-ref-counted-target-assigned-shared.patch (4K) Download Attachment
xsa276/0001-x86-hvm-ioreq-fix-page-referencing.patch (5K) Download Attachment
xsa276/0002-x86-hvm-ioreq-use-ref-counted-target-assigned-shared.patch (4K) Download Attachment
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