Bug 1272371 (CVE-2015-7872)

Summary:	CVE-2015-7872 kernel: Keyrings crash triggerable by unprivileged user
Product:	[Other] Security Response	Reporter:	Adam Mariš <amaris>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	aquini, arm-mgr, bhu, blc, carnil, dhoward, fhrbata, gansalmon, iboverma, itamar, jbastian, jforbes, jindrich.novy, jkacur, joelsmith, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, kstutsma, lgoncalv, madhu.chinakonda, matt, mchehab, mcressma, mlangsdo, mrg-program-list, nmurray, plougher, pmatouse, rt-maint, rvrbovsk, slawomir, slong, vgoyal, vvs, williams, wmealing
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:	It was found that the Linux kernel's keys subsystem did not correctly garbage collect uninstantiated keyrings. A local attacker could use this flaw to crash the system or, potentially, escalate their privileges on the system.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-06-08 02:44:10 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:	1272172, 1273463, 1273465, 1275926, 1275927, 1275928, 1275929, 1275930, 1275931, 1275932, 1275933, 1275934, 1291660
Bug Blocks:	1272373

Description Adam Mariš 2015-10-16 09:35:42 UTC

A vulnerability in the Linux kernel's keyrings garbage collector allowing any local user account to trigger a kernel panic.

Problem arrises when using request_key() or keyctl request2.

This code sequence tries to invoke an upcall to instantiate a keyring if one doesn't already exist by that name within the user's keyring set. However, if the upcall fails, the code sets keyring->type_data.reject_error to -ENOKEY or some other error code.  When the key is garbage collected, the key destroy function is called unconditionally and keyring_destroy() uses list_empty() on keyring->type_data.link - which is in a union with reject_error. Subsequently, the kernel tries to unlink the keyring from the keyring names list, which leads to an oops.

Comment 1 Adam Mariš 2015-10-20 10:56:28 UTC

Upstream patch:

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ce1fad2740c648a4340f6f6c391a8a83769d2e8c

Comment 2 Adam Mariš 2015-10-20 11:43:54 UTC

CVE request:

http://seclists.org/oss-sec/2015/q4/111

Comment 4 Wade Mealing 2015-10-30 05:41:58 UTC

Statement:

This issue affects the Linux kernels as shipped with Red Hat Enterprise Linux 6 , 7 and Red Hat MRG 2. Future updates for the respective releases may address this flaw.

Comment 10 errata-xmlrpc 2015-12-15 13:59:25 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2015:2636 https://rhn.redhat.com/errata/RHSA-2015-2636.html

Comment 12 errata-xmlrpc 2016-02-16 10:48:55 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2016:0212 https://rhn.redhat.com/errata/RHSA-2016-0212.html

Comment 13 errata-xmlrpc 2016-02-16 11:19:17 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2016:0185 https://rhn.redhat.com/errata/RHSA-2016-0185.html

Comment 14 errata-xmlrpc 2016-02-16 15:05:22 UTC

This issue has been addressed in the following products:

  MRG for RHEL-6 v.2

Via RHSA-2016:0224 https://rhn.redhat.com/errata/RHSA-2016-0224.html