Bug 1411245 (CVE-2015-8963)

Summary:	CVE-2015-8963 kernel: Race condition on CPU unplug leading to use-after-free
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	aquini, bhu, dhoward, fhrbata, gansalmon, iboverma, ichavero, itamar, jforbes, jkacur, joelsmith, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, lgoncalv, madhu.chinakonda, mchehab, mcressma, nmurray, pholasek, rt-maint, rvrbovsk, williams, wmealing, yozone
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	kernel 4.4	Doc Type:	If docs needed, set a value
Doc Text:	Race condition in kernel/events/core.c in the Linux kernel before 4.4 allows local users to gain privileges or cause a denial of service via use-after-free vulnerability by leveraging incorrect handling of an swevent data structure during a CPU unplug operation.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-10-27 10:52:04 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1449476, 1449477
Bug Blocks:	1395262

Description Adam Mariš 2017-01-09 09:04:20 UTC

Race condition in kernel/events/core.c in the Linux kernel before 4.4 allows local users to gain privileges or cause a denial of service via use-after-free vulnerability by leveraging incorrect handling of an swevent data structure during a CPU unplug operation.

Removing a CPU is a privileged operation and not possible by normal users.  This flaw should not affect many individuals.

Upstream patch:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=12ca6ad2e3a896256f086497a7c7406a547ee373

Comment 2 Wade Mealing 2017-05-10 05:51:21 UTC

Statement:

This issue affects the Linux kernel shipping with Red Hat Enterprise Linux 6. Future updates for the respective releases may address the issue.

This issue does not not affect Red Hat Enterprise Linux 5, 7, MRG-2 kernels.

This has been rated as having Moderate security impact and is not currently planned to be addressed in future updates of Red Hat Enterprise Linux 5. For additional information, refer to the Red Hat Enterprise Linux Life Cycle: https://access.redhat.com/support/policy/updates/errata/.

Comment 3 Wade Mealing 2017-05-10 05:59:41 UTC

Mitigation:

A possible mitigation is to only remove CPU's while the system is shut down.  This will prevent local attackers from being able to abuse this flaw.