Bug 1568744 (CVE-2018-1000200)

Summary:	CVE-2018-1000200 kernel: NULL pointer dereference on OOM kill of large mlocked process
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:	airlied, aquini, bhu, blc, bskeggs, dhoward, ewk, fhrbata, hdegoede, hkrzesin, hwkernel-mgr, iboverma, ichavero, itamar, jarodwilson, jforbes, jglisse, jkacur, john.j5live, jonathan, josef, jross, jwboyer, kernel-maint, kernel-mgr, labbott, lgoncalv, linville, matt, mchehab, mcressma, mjg59, mlangsdo, nmurray, plougher, rt-maint, rvrbovsk, security-response-team, skozina, steved, vdronov, williams, wmealing
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in the Linux kernel where an out of memory (oom) killing of a process that has large spans of mlocked memory can result in deferencing a NULL pointer, leading to denial of service.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-06-10 10:20:05 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:	1570542, 1571595, 1571596
Bug Blocks:	1568749

Description Adam Mariš 2018-04-18 08:29:27 UTC

It was found that out of memory (oom) killing a process that has large spans of mlocked memory can result in deferencing a NULL pointer, leading to denial of service.

The issue arises from an oom killed process's final thread calling exit_mmap(), which calls munlock_vma_pages_all() for mlocked vmas.  This can happen synchronously with the oom reaper's unmap_page_range() since the vma's VM_LOCKED bit is cleared before munlocking (to determine if any other vmas share the memory and are mlocked).

References: 

https://marc.info/?l=linux-kernel&m=152400522806945

https://marc.info/?l=linux-kernel&m=152460926619256

http://seclists.org/oss-sec/2018/q2/67

Introduced by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=212925802454672e6cd2949a727f5e2c1377bf06

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=27ae357fa82be5ab73b2ef8d39dcb8ca2563483a

Comment 1 Adam Mariš 2018-04-18 08:29:30 UTC

Acknowledgments:

Name: David Rientjes (Google)

Comment 6 Adam Mariš 2018-04-25 07:58:22 UTC

Public via:

http://seclists.org/oss-sec/2018/q2/67

Comment 7 Adam Mariš 2018-04-25 07:59:21 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1571596]

Comment 9 Justin M. Forbes 2018-04-25 12:17:05 UTC

This was fixed for Fedora with the 4.15 rebases

Comment 12 errata-xmlrpc 2018-10-30 09:00:04 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2018:2948 https://access.redhat.com/errata/RHSA-2018:2948