Bug 1249849 (CVE-2015-4178)

Summary:	CVE-2015-4178 kernel: list corruption of m_list or s_list if unused
Product:	[Other] Security Response	Reporter:	Wade Mealing <wmealing>
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, 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, plougher, rt-maint, rvrbovsk, slawomir, slong, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:	A flaw was found in the Linux kernel which is related to the user namespace lazily unmounting file systems. The fs_pin struct has two members (m_list and s_list) which are usually initialized on use in the pin_insert_group function. However, these members might go unmodified; in this case, the system panics when it attempts to destroy or free them. This flaw could be used to launch a denial-of-service attack.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-01-20 02:00:05 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:
Bug Blocks:	1224245

Description Wade Mealing 2015-08-04 00:49:32 UTC

A flaw was found in the linux kernel related to the user namespace
lazily unmounting filesystems.  The fs_pin struct had two members
(m_list and s_list) which are usually initialized on use in the pin_insert_group function.

It is possible that these lists go unmodified and are then attempted to be 
destroyed/freed panicing the system.

Upstream patch:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=820f9f147dcce2602eefd9b575bbbd9ea14f0953


CVE Request:
http://seclists.org/oss-sec/2015/q2/640

Comment 1 Wade Mealing 2015-08-20 03:53:33 UTC

Statement:

This issue does not affect the Linux kernels as shipped with Red Hat Enterprise Linux 5, 6, 7, MRG-2, realtime and arm-kernels.