Bug 1832543 (CVE-2020-12655)

Summary:	CVE-2020-12655 kernel: sync of excessive duration via an XFS v5 image with crafted metadata
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED ERRATA	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	acaringi, airlied, bhu, blc, bmasney, brdeoliv, bskeggs, dhoward, dvlasenk, esammons, fhrbata, hdegoede, hkrzesin, iboverma, ichavero, itamar, jarodwilson, jeremy, jforbes, jglisse, jlelli, john.j5live, jonathan, josef, jross, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, kyoshida, labbott, lgoncalv, linville, masami256, matt, mchehab, mcressma, mjg59, mlangsdo, nmurray, ptalbert, qzhao, rt-maint, rvrbovsk, steved, 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 discovered in the XFS source in the Linux kernel. This flaw allows an attacker with the ability to mount an XFS filesystem, to trigger a denial of service while attempting to sync a file located on an XFS v5 image with crafted metadata.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-08-25 19:17:46 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:	1832545, 1837191, 1837192, 1837193, 1837194, 1837195
Bug Blocks:	1832546

Description Guilherme de Almeida Suckevicz 2020-05-06 19:41:04 UTC

An issue was discovered in xfs_agf_verify in fs/xfs/libxfs/xfs_alloc.c in the Linux kernel. An attacker who is able to mount a xfs filesystem can trigger a denial of service while attempting to sync a file located an XFS v5 image with crafted metadata.

Reference and upstream commit:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d0c7feaf87678371c2c09b3709400be416b2dc62
https://lore.kernel.org/linux-xfs/20200221153803.GP9506@magnolia/

Comment 1 Guilherme de Almeida Suckevicz 2020-05-06 19:43:08 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1832545]

Comment 4 Wade Mealing 2020-05-19 03:45:41 UTC

Mitigation:


This flaw requires an attacker being able to have the system mount a crafted filesystem.

If the xfs filesystem is not in use, the 'xfs' kernel module can be blacklisted and the module
will not be loaded when the filesystem is mounted, mounting will fail.

However, if this filesystem is in use, this workaround will not be suitable.

To find out how to blacklist the "xfs" kernel module please see https://access.redhat.com/solutions/41278 or contact Red hat Global Support services

Comment 8 Petr Matousek 2020-05-26 12:20:47 UTC

Statement:

This issue is rated as having Low impact because of the preconditions needed to trigger it (administrative account or physical access).

Comment 9 errata-xmlrpc 2020-08-25 13:13:36 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2020:3545 https://access.redhat.com/errata/RHSA-2020:3545

Comment 10 Product Security DevOps Team 2020-08-25 19:17:46 UTC

This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2020-12655

Comment 11 errata-xmlrpc 2020-11-04 00:51:00 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2020:4431 https://access.redhat.com/errata/RHSA-2020:4431

Comment 12 errata-xmlrpc 2020-11-04 02:23:27 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2020:4609 https://access.redhat.com/errata/RHSA-2020:4609