Bug 1256746

Summary:	CVE-2015-6666 kernel: Linux x86_64 NT flag handling optimization allowing DoS
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	agordeev, aquini, arm-mgr, bhu, bz-reply, dhoward, esammons, fhrbata, gansalmon, iboverma, itamar, jforbes, jkacur, joelsmith, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, lgoncalv, lwang, madhu.chinakonda, matt, mchehab, mcressma, mguzik, nmurray, pholasek, plougher, pmatouse, rt-maint, rvrbovsk, williams
Target Milestone:	---	Keywords:	Reopened, Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-09-26 03:37:19 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:	1256753
Bug Blocks:	1256750

Description Adam Mariš 2015-08-25 11:40:33 UTC

After fixing Linux's NT flag handling, an optimization was added, making the code vulnerable.
A malicious 32-bit program might be able to leak NT into an unrelated task.
On a kernel with setting CONFIG_PREEMPT=y, this causes a straightforward DoS. With CONFIG_PREEMPT=n setting,
it's probably still exploitable for DoS with some more care.
This vulnerability could be possibly used also for privilege escalation.

Upstream fix (just reverting the optimization):

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=512255a2ad2c832ca7d4de9f31245f73781922d0

CVE assignment:

http://seclists.org/oss-sec/2015/q3/430

Can be mitigated by:

CONFIG_IA32_EMULATION=n

Mitigation:

(none)

Comment 1 Adam Mariš 2015-08-25 12:03:54 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1256753]

Comment 2 Fedora Update System 2015-08-25 12:53:57 UTC

kernel-4.2.0-0.rc8.git0.1.fc23 has been submitted as an update to Fedora 23. https://bodhi.fedoraproject.org/updates/FEDORA-2015-14151

Comment 3 Fedora Update System 2015-08-27 17:57:21 UTC

kernel-4.2.0-0.rc8.git0.1.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.

Comment 4 Fedora Update System 2015-09-11 17:21:18 UTC

kernel-4.1.6-201.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.

Comment 5 Martin Prpič 2015-09-15 07:58:27 UTC

This was found to not have a security impact on any version of the Linux kernel. This CVE may be rejected as per:

http://seclists.org/oss-sec/2015/q3/546

Comment 6 Martin Prpič 2015-09-21 06:20:36 UTC

CVE-2015-6666 was rejected, removing alias.

Comment 7 Fedora Update System 2015-09-23 00:20:20 UTC

kernel-4.1.7-100.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.