An issue was discovered in Xen 4.14.x. There is a missing unlock in the XENMEM_acquire_resource error path. The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar to forgetting to unlock a spinlock. A buggy or malicious HVM stubdomain can cause an RCU reference to be leaked. This causes subsequent administration operations, (e.g., CPU offline) to livelock, resulting in a host Denial of Service. The buggy codepath has been present since Xen 4.12. Xen 4.14 and later are vulnerable to the DoS. The side effects are believed to be benign on Xen 4.12 and 4.13, but patches are provided nevertheless. The vulnerability can generally only be exploited by x86 HVM VMs, as these are generally the only type of VM that have a Qemu stubdomain. x86 PV and PVH domains, as well as ARM VMs, typically don't use a stubdomain. Only VMs using HVM stubdomains can exploit the vulnerability. VMs using PV stubdomains, or with emulators running in dom0, cannot exploit the vulnerability.

A denial of service (DoS) vulnerability exists in Xen servers XENMEM_acquire_resource due to an error path exiting without releasing an RCU (Read, Copy, Update) reference. An authenticated, local attacker can exploit this issue, via a malicious HVM stubdomain which can cause an RCU reference to be leaked, that leads to subsequent administration operations, (e.g. CPU offline) to livelock, resulting in a host DoS.

This update for xen fixes the following issues :

CVE-2020-25602: Fixed an issue where there was a crash when handling guest access to MSR_MISC_ENABLE was thrown (bsc#1176339,XSA-333)

CVE-2020-25598: Added a missing unlock in XENMEM_acquire_resource error path (bsc#1176341,XSA-334)

CVE-2020-25604: Fixed a race condition when migrating timers between x86 HVM vCPU-s (bsc#1176343,XSA-336)

CVE-2020-25595: Fixed an issue where PCI passthrough code was reading back hardware registers (bsc#1176344,XSA-337)

CVE-2020-25597: Fixed an issue where a valid event channels may not turn invalid (bsc#1176346,XSA-338)

CVE-2020-25596: Fixed a potential denial of service in x86 pv guest kernel via SYSENTER (bsc#1176345,XSA-339)

CVE-2020-25603: Fixed an issue due to missing barriers when accessing/allocating an event channel (bsc#1176347,XSA-340)

CVE-2020-25600: Fixed out of bounds event channels available to 32-bit x86 domains (bsc#1176348,XSA-342)

CVE-2020-25599: Fixed race conditions with evtchn_reset() (bsc#1176349,XSA-343)

CVE-2020-25601: Fixed an issue due to lack of preemption in evtchn_reset() / evtchn_destroy() (bsc#1176350,XSA-344)

CVE-2020-14364: Fixed an out-of-bounds read/write access while processing usb packets (bsc#1175534).

Various bug fixes (bsc#1027519)

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.

This update for xen fixes the following issues :

CVE-2020-25602: Fixed an issue where there was a crash when handling guest access to MSR_MISC_ENABLE was thrown (bsc#1176339,XSA-333)

CVE-2020-25598: Added a missing unlock in XENMEM_acquire_resource error path (bsc#1176341,XSA-334)

CVE-2020-25604: Fixed a race condition when migrating timers between x86 HVM vCPU-s (bsc#1176343,XSA-336)

CVE-2020-25595: Fixed an issue where PCI passthrough code was reading back hardware registers (bsc#1176344,XSA-337)

CVE-2020-25597: Fixed an issue where a valid event channels may not turn invalid (bsc#1176346,XSA-338)

CVE-2020-25596: Fixed a potential denial of service in x86 pv guest kernel via SYSENTER (bsc#1176345,XSA-339)

CVE-2020-25603: Fixed an issue due to missing barriers when accessing/allocating an event channel (bsc#1176347,XSA-340)

CVE-2020-25600: Fixed out of bounds event channels available to 32-bit x86 domains (bsc#1176348,XSA-342)

CVE-2020-25599: Fixed race conditions with evtchn_reset() (bsc#1176349,XSA-343)

CVE-2020-25601: Fixed an issue due to lack of preemption in evtchn_reset() / evtchn_destroy() (bsc#1176350,XSA-344)

Various other fixes (bsc#1027519)

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.

This update for xen fixes the following issues :

CVE-2020-25602: Fixed an issue where there was a crash when handling guest access to MSR_MISC_ENABLE was thrown (bsc#1176339,XSA-333)

CVE-2020-25598: Added a missing unlock in XENMEM_acquire_resource error path (bsc#1176341,XSA-334)

CVE-2020-25604: Fixed a race condition when migrating timers between x86 HVM vCPU-s (bsc#1176343,XSA-336)

CVE-2020-25595: Fixed an issue where PCI passthrough code was reading back hardware registers (bsc#1176344,XSA-337)

CVE-2020-25597: Fixed an issue where a valid event channels may not turn invalid (bsc#1176346,XSA-338)

CVE-2020-25596: Fixed a potential denial of service in x86 pv guest kernel via SYSENTER (bsc#1176345,XSA-339)

CVE-2020-25603: Fixed an issue due to missing barriers when accessing/allocating an event channel (bsc#1176347,XSA-340)

CVE-2020-25600: Fixed out of bounds event channels available to 32-bit x86 domains (bsc#1176348,XSA-342)

CVE-2020-25599: Fixed race conditions with evtchn_reset() (bsc#1176349,XSA-343)

CVE-2020-25601: Fixed an issue due to lack of preemption in evtchn_reset() / evtchn_destroy() (bsc#1176350,XSA-344)

Various bug fixes (bsc#1027519)

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 remote host is affected by the vulnerability described in GLSA-202011-06 (Xen: Multiple vulnerabilities)

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

    Please review the referenced CVE identifiers for details.
  Workaround :

    There is no known workaround at this time.

x86 pv: Crash when handling guest access to MSR_MISC_ENABLE [XSA-333, CVE-2020-25602] (#1881619) Missing unlock in XENMEM_acquire_resource error path [XSA-334, CVE-2020-25598] (#1881616) race when migrating timers between x86 HVM vCPU-s [XSA-336, CVE-2020-25604] (#1881618) PCI passthrough code reading back hardware registers [XSA-337, CVE-2020-25595] (#1881587) once valid event channels may not turn invalid [XSA-338, CVE-2020-25597] (#1881588) x86 pv guest kernel DoS via SYSENTER [XSA-339, CVE-2020-25596] (#1881617) Missing memory barriers when accessing/allocating an event channel [XSA-340, CVE-2020-25603] (#1881583) out of bounds event channels available to 32-bit x86 domains [XSA-342, CVE-2020-25600] (#1881582) races with evtchn_reset() [XSA-343, CVE-2020-25599] (#1881581) lack of preemption in evtchn_reset() / evtchn_destroy() [XSA-344, CVE-2020-25601] (#1881586)

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

This update for xen fixes the following issues :

  - CVE-2020-25602: Fixed an issue where there was a crash     when handling guest access to MSR_MISC_ENABLE was thrown     (bsc#1176339,XSA-333)

  - CVE-2020-25598: Added a missing unlock in     XENMEM_acquire_resource error path (bsc#1176341,XSA-334)

  - CVE-2020-25604: Fixed a race condition when migrating     timers between x86 HVM vCPU-s (bsc#1176343,XSA-336)

  - CVE-2020-25595: Fixed an issue where PCI passthrough     code was reading back hardware registers     (bsc#1176344,XSA-337)

  - CVE-2020-25597: Fixed an issue where a valid event     channels may not turn invalid (bsc#1176346,XSA-338)

  - CVE-2020-25596: Fixed a potential denial of service in     x86 pv guest kernel via SYSENTER (bsc#1176345,XSA-339)

  - CVE-2020-25603: Fixed an issue due to missing barriers     when accessing/allocating an event channel     (bsc#1176347,XSA-340)

  - CVE-2020-25600: Fixed out of bounds event channels     available to 32-bit x86 domains (bsc#1176348,XSA-342)

  - CVE-2020-25599: Fixed race conditions with     evtchn_reset() (bsc#1176349,XSA-343)

  - CVE-2020-25601: Fixed an issue due to lack of preemption     in evtchn_reset() / evtchn_destroy()     (bsc#1176350,XSA-344)

  - Various other fixes (bsc#1027519)

This update was imported from the SUSE:SLE-15-SP2:Update update project.

ID	Name	Product	Family	Severity
144794	XENMEM_aquire_resources Error Path DoS (XSA-334)	Nessus	Misc.	medium
143853	SUSE SLES12 Security Update : xen (SUSE-SU-2020:2788-1)	Nessus	SuSE Local Security Checks	high
143707	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:2791-1)	Nessus	SuSE Local Security Checks	high
143685	SUSE SLES12 Security Update : xen (SUSE-SU-2020:2786-1)	Nessus	SuSE Local Security Checks	high
143637	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:2790-1)	Nessus	SuSE Local Security Checks	high
142854	GLSA-202011-06 : Xen: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
141278	Fedora 31 : xen (2020-d46fe34349)	Nessus	Fedora Local Security Checks	high
141270	Fedora 33 : xen (2020-306b84fd07)	Nessus	Fedora Local Security Checks	high
141168	openSUSE Security Update : xen (openSUSE-2020-1608)	Nessus	SuSE Local Security Checks	high
141102	Fedora 32 : xen (2020-f668e579be)	Nessus	Fedora Local Security Checks	high

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CVE-2020-25598

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