Bug 1980069 (CVE-2021-35039)

Summary:	CVE-2021-35039 kernel: allows loading unsigned kernel modules via init_module syscall
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
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, bhu, blc, brdeoliv, bskeggs, chwhite, crwood, dhoward, dvlasenk, fhrbata, fpacheco, hdegoede, hkrzesin, jarod, 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, walters, wcosta, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	Linux kernel 5.13	Doc Type:	If docs needed, set a value
Doc Text:	A flaw incorrect handle of boot param module.sig_enforce=1 in the Linux kernel modules sign verification functionality was found in the way user boot with this param enabled and both if kernel compiled with param CONFIG_MODULE_SIG unset, then user still can load unsigned module even param module.sig_enforce pretending to be enabled. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-08-03 15:49:09 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:	1980070, 1980433
Bug Blocks:	1980071

Description Guilherme de Almeida Suckevicz 2021-07-07 17:17:36 UTC

kernel/module.c in the Linux kernel before 5.12.14 mishandles Signature Verification. Without CONFIG_MODULE_SIG, verification that a kernel module is signed, for loading via init_module, does not occur for a module.sig_enforce=1 command-line argument.

Reference:
https://www.openwall.com/lists/oss-security/2021/07/06/3

Upstream patch:
https://github.com/torvalds/linux/commit/0c18f29aae7ce3dadd26d8ee3505d07cc982df75

Comment 1 Guilherme de Almeida Suckevicz 2021-07-07 17:18:06 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1980070]

Comment 2 Justin M. Forbes 2021-07-08 13:59:33 UTC

Fedora enables MODULE_SIG so should not be vulnerable to this, The patch is included in the stable update 5.12.14 for Fedora, so users building their own configs should be covered there as well.