Bug 1950499 (CVE-2021-3492)

Summary:	CVE-2021-3492 kernel: shiftfs file system double free vulnerability
Product:	[Other] Security Response	Reporter:	Pedro Sampaio <psampaio>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, adscvr, airlied, alciregi, bdettelb, bhu, blc, bmasney, brdeoliv, bskeggs, chwhite, crwood, dhoward, dvlasenk, fhrbata, fpacheco, hdegoede, hkrzesin, jarodwilson, jeremy, jforbes, jglisse, jlelli, jonathan, josef, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, masami256, mchehab, mlangsdo, nmurray, ptalbert, qzhao, rvrbovsk, steved, tomckay, walters, wcosta, 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:	A flaw use after free (or use before allocation) in the Linux kernel Shiftfs file-system was found in the way user calls one of the few ioctls. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-04-29 12:24:10 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:	1950503
Bug Blocks:	1950504

Description Pedro Sampaio 2021-04-16 18:31:47 UTC

It was discovered that shiftfs, when passing through ioctls to the underlying file system, did not properly handle faults occurring during copy_from_user() correctly, leading to a double-free vulnerability or not freeing memory at all. An attacker could use this to cause a denial of service (memory consumption) or execute arbitrary code.

References:

https://www.openwall.com/lists/oss-security/2021/04/16/2

Comment 1 Pedro Sampaio 2021-04-16 18:32:58 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1950503]

Comment 2 Justin M. Forbes 2021-04-16 20:52:39 UTC

"Shiftfs is an out-of-tree stacking file system for the Linux kernel
included in Ubuntu kernels"

Fedora does not carry this patch set.

Comment 4 Alex 2021-04-26 15:31:00 UTC

Statement:

Shiftfs has not been accepted in the upstream Linux kernel. It is both non included to the any versions of the Red Hat Enterprise Linux.