Bug 703972 (CVE-2011-1781)

Summary:	CVE-2011-1781 systemtap: divide by zero stack unwinding flaw
Product:	[Other] Security Response	Reporter:	Josh Bressers <bressers>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	fche, mjc, mjw, pmuller, scox, security-response-team
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:	2012-02-03 20:45:31 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:	703979, 703980
Bug Blocks:

Description Josh Bressers 2011-05-11 19:30:50 UTC

A flaw was discovered in systemtap's handling of DWARF expressions where it
did not guard against divide by zero when unwinding the stack.  This can
result in a kernel div-by-zero message and possible busywait during stap
module shutdown.  A div-by-zero could cause the kernel to panic and if the
kernel reboot on panic flag was set (panic_on_oops), it would cause the
system to reboot.

In order to trigger this flaw, an admin would have to enable unprivileged
mode. If an admin has enabled unprivileged mode, a normal user could use
this to crash the target machine.

A workaround is to disable unprivileged mode.

Comment 1 Josh Bressers 2011-05-11 19:32:57 UTC

This bug only affects systemtap versions 1.4 and above. We are rebasing systemtap to an affected version in Red Hat Enterprise Linux 6.1. This flaw will not be fixed before 6.1 GA.

Comment 3 Frank Ch. Eigler 2011-05-11 23:34:29 UTC

Fixed upstream:

http://sourceware.org/git/?p=systemtap.git;a=commit;h=fa2e3415185a28542d419a641ecd6cddd52e3cd9

Comment 4 Frank Ch. Eigler 2011-05-11 23:35:31 UTC

"If an admin has enabled unprivileged mode, a normal user could use
this to crash the target machine."

Not quite "normal" - the user would still have to be member of the "stapusr" group.

Comment 5 Tomas Hoger 2011-05-20 11:53:23 UTC

Public now via upstream commit mentioned in comment #3.

Comment 9 errata-xmlrpc 2011-05-31 14:04:51 UTC

This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2011:0842 https://rhn.redhat.com/errata/RHSA-2011-0842.html