Bug 2112688 (CVE-2020-36557)

Summary:	CVE-2020-36557 kernel: race condition between the VT_DISALLOCATE ioctl and closing/opening of ttys, causing a use-after-free in con_shutdown().
Product:	[Other] Security Response	Reporter:	Alex <allarkin>
Component:	vulnerability	Assignee:	Nobody <nobody>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, adscvr, airlied, alciregi, bdettelb, bhu, brdeoliv, chwhite, crwood, ddepaula, dvlasenk, hdegoede, hkrzesin, hpa, jarod, jarodwilson, jburrell, jfaracco, jferlan, jforbes, jglisse, jlelli, joe.lawrence, jonathan, josef, jshortt, jstancek, jwboyer, jwyatt, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, lzampier, masami256, mchehab, nmurray, ptalbert, qzhao, rvrbovsk, scweaver, steved, tyberry, vkumar, walters, 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 use-after-free flaw was found in the Linux kernel’s Virtual Terminal subsystem in how a user calls the VT_DISALLOCATE ioctl during the closing/opening of ttys. This flaw allows a local user to crash the system.	Story Points:	---
Clone Of:		Environment:
Last Closed:		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:	1875585, 2112689, 2112690, 2112691, 2112692, 2183122, 2183123, 2183124, 2183125
Bug Blocks:	2109700

Description Alex 2022-07-31 17:10:52 UTC

A use-after-free vulnerability was found in drivers/tty/vt/vt.c in the Linux kernel before 5.6.2.
A race condition between the VT_DISALLOCATE ioctl and closing/opening of ttys could lead to a use-after-free in con_shutdown().

Reference:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ca4463bf8438b403596edd0ec961ca0d4fbe0220