Bug 1427239 (CVE-2017-5669)

Summary:	CVE-2017-5669 kernel: Shmat allows mmap null page protection bypass
Product:	[Other] Security Response	Reporter:	Andrej Nemec <anemec>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	agordeev, anemec, aquini, bhu, dhoward, esammons, fhrbata, gansalmon, iboverma, ichavero, itamar, jforbes, jkacur, jkastner, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, labbott, lgoncalv, lwang, madhu.chinakonda, matt, mchehab, mcressma, mguzik, nmurray, pholasek, plougher, rt-maint, rvrbovsk, sparks, vdronov, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	The do_shmat function in ipc/shm.c in the Linux kernel, through 4.9.12, does not restrict the address calculated by a certain rounding operation. This allows privileged local users to map page zero and, consequently, bypass a protection mechanism that exists for the mmap system call. This is possible by making crafted shmget and shmat system calls in a privileged context.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2017-03-16 16:49:01 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:	1427241

Description Andrej Nemec 2017-02-27 16:28:02 UTC

The do_shmat function in ipc/shm.c in the Linux kernel does not restrict the address calculated by a certain rounding operation, which allows local users to map page zero, and consequently bypass a protection mechanism that exists for the mmap system call, by making crafted shmget and shmat system calls in a privileged context.

Upstream bug:

https://bugzilla.kernel.org/show_bug.cgi?id=192931

Upstream patch:

https://github.com/torvalds/linux/commit/e1d35d4dc7f089e6c9c080d556feedf9c706f0c7

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=95e91b831f87ac8e1f8ed50c14d709089b4e01b8

Comment 1 Fedora Update System 2017-03-11 11:51:39 UTC

kernel-4.9.13-101.fc24 has been pushed to the Fedora 24 stable repository. If problems still persist, please make note of it in this bug report.

Comment 4 Vladis Dronov 2017-03-16 16:49:01 UTC

Statement:

This issue does not affect the Linux kernel packages as shipped with Red Hat Enterprise Linux 5, 6, 7 and Red Hat Enterprise MRG-2 as the flaw can only be exploited by a privileged user.