Bug 659567 (CVE-2010-4258)

Summary:	CVE-2010-4258 kernel: failure to revert address limit override in OOPS error path
Product:	[Other] Security Response	Reporter:	Eugene Teo (Security Response) <eteo>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	anderson, arozansk, bhu, cye, dhoward, jkacur, jolsa, kernel-mgr, kmcmartin, lgoncalv, lwang, plyons, rkhan, rt-maint, tcallawa, vgoyal, vkrizan, vmayatsk, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-07-29 13:28:12 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	659568, 659569, 659570, 659571, 659572, 659573, 659574
Bug Blocks:

Description Eugene Teo (Security Response) 2010-12-03 02:04:48 UTC

Nelson discovered an interesting interaction in the Linux kernel between the clear_child_tid feature of clone(2), and the set_fs() function used internally in the kernel to temporarily disable access_ok() checking of userspace pointers.

Under some (not totally uncommon) circumstances, it is possible for a user to leverage this interaction to turn a kernel oops or BUG() into a write of an integer 0 to a user-controlled address in kernel memory.

This is known to be exploited with CVE-2010-3849 - http://www.redhat.com/security/data/cve/CVE-2010-3849.html.

Acknowledgements:

Red Hat would like to thank Nelson Elhage for reporting this issue.

Comment 2 Eugene Teo (Security Response) 2010-12-06 02:49:06 UTC

This needs oops to first trigger the mm_release path with set_fs(KERNEL_DS) and invoke put_user(0, tsk->clear_child_tid). We have panic_on_oops set on rhel so this is not exploitable because mm_release will not get called and the box panics.

Comment 4 Eugene Teo (Security Response) 2010-12-06 02:58:58 UTC

Statement:

The Linux kernel as shipped with Red Hat Enterprise Linux 4, 5, 6, and Red Hat Enterprise MRG enabled the panic_on_oops sysctl tunable by default, and therefore are not affected by this issue. However, as a preventive measure (for example, for administrators who have turned panic_on_oops off), this issue was fixed in kernel updates in Red Hat Enterprise Linux 4, 5, 6, and Red Hat Enterprise MRG. Because the fix was considered as a preventative measure, this CVE is not listed in the related advisories that provided the fix: RHSA-2011:0162, RHSA-2011:0263, RHSA-2011:0017, RHSA-2011:0498, RHSA-2011:0542, RHSA-2011:0330. The fix is documented in each of these advisories as a regular bug fix, for example as BZ#659568 in RHSA-2011:0162.