Bug 1899177 (CVE-2020-28915)

Summary:	CVE-2020-28915 kernel: out-of-bounds read in fbcon_get_font function
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:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, adscvr, airlied, bhu, blc, bmasney, bskeggs, cchung, dhoward, dvlasenk, fhrbata, hdegoede, hkrzesin, iboverma, itamar, jarod, jarodwilson, jeremy, jforbes, jlelli, jonathan, josef, jross, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, masami256, mchehab, mcressma, mjg59, mlangsdo, nmurray, ptalbert, qzhao, rkeshri, rt-maint, rvrbovsk, steved, walters, williams, yozone
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	An out-of-bounds (OOB) memory access flaw was found in fbcon_get_font() in drivers/video/fbdev/core/fbcon.c in fbcon driver module in the Linux kernel. A bound check failure allows a local attacker with special user privilege to gain access to out-of-bounds memory, leading to a system crash or a leak of internal kernel information. The highest threat from this vulnerability is to integrity and system availability.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-12-03 17:03:21 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:	1899178, 1904373, 1904374, 1904375, 1904376, 1904377, 2064762, 2076348
Bug Blocks:	1899179

Description Guilherme de Almeida Suckevicz 2020-11-18 16:43:35 UTC

An out-of-bounds (OOB) memory access flaw was found in fbcon_get_font() in drivers/video/fbdev/core/fbcon.c in fbcon driver module in the Linux kernel. A bound check failure may allow a local attacker with special user privilege to gain access to out-of-bounds memory leading to a system crash or a leak of internal kernel information. The highest threat from this vulnerability is to system availability.

Reference:
https://syzkaller.appspot.com/bug?id=08b8be45afea11888776f897895aef9ad1c3ecfd

Comment 1 Guilherme de Almeida Suckevicz 2020-11-18 16:45:00 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1899178]

Comment 2 Justin M. Forbes 2020-11-18 17:39:09 UTC

This was fixed for Fedora with the 5.8.15 stable kernel updates.

Comment 10 Rohit Keshri 2020-12-12 17:17:08 UTC

Mitigation:

Add 'nomodeset' option as kernel boot parameter to disable frame buffering (edit /etc/default/grub, and run 'grub2-mkconfig -o /boot/grub2/grub.cfg' and reboot).
~~~
# cat /proc/cmdline 
BOOT_IMAGE=(hd0,msdos1)/vmlinuz-4.18.0-147.el8.x86_64 root=/dev/mapper/rhel_rhel8u2--1-root ro crashkernel=auto resume=/dev/mapper/rhel_rhel8u2--1-swap rd.lvm.lv=rhel_rhel8u2-1/root rd.lvm.lv=rhel_rhel8u2-1/swap nomodeset

# ls -l /dev/fb*
ls: cannot access '/dev/fb*': No such file or directory
~~~

Comment 28 errata-xmlrpc 2022-06-28 12:25:50 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2022:5344 https://access.redhat.com/errata/RHSA-2022:5344

Comment 29 errata-xmlrpc 2022-06-28 18:31:53 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2022:5316 https://access.redhat.com/errata/RHSA-2022:5316

Comment 34 Product Security DevOps Team 2022-12-03 17:03:16 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-2020-28915