Bug 1814237 (CVE-2020-9391)

Summary:	CVE-2020-9391 kernel: brk discards top byte of addresses on aarch64 causing heap corruption in glibc malloc
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, airlied, bdettelb, bhu, blc, brdeoliv, bskeggs, dhoward, dvlasenk, esammons, fhrbata, hdegoede, hkrzesin, iboverma, ichavero, itamar, jarodwilson, jeremy, jforbes, jglisse, jlelli, john.j5live, jonathan, josef, jross, jschorr, jshortt, jstancek, jwboyer, kernel-maint, kernel-mgr, labbott, lgoncalv, linville, masami256, matt, mchehab, mcressma, mjg59, mlangsdo, nmurray, qzhao, rt-maint, rvrbovsk, steved, 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 heap corruption flaw was found in the Linux kernel on the AArch64 architecture. The top byte is ignored in the address passed to the brk system call, potentially moving the memory break downwards when the application expects it to move upwards. This has been observed to cause heap corruption within the GNU C Library malloc implementation. The highest threat from this vulnerability is to system availability.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-03-23 16:32:17 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:	1797052, 1814238
Bug Blocks:	1805473

Description Guilherme de Almeida Suckevicz 2020-03-17 12:51:08 UTC

An issue was discovered in the Linux kernel 5.4 and 5.5 through 5.5.6 on the AArch64 architecture. It ignores the top byte in the address passed to the brk system call, potentially moving the memory break downwards when the application expects it to move upwards, aka CID-dcde237319e6. This has been observed to cause heap corruption with the GNU C Library malloc implementation.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=1797052
http://www.openwall.com/lists/oss-security/2020/02/25/6

Upstream commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dcde237319e626d1ec3c9d8b7613032f0fd4663a

Comment 1 Guilherme de Almeida Suckevicz 2020-03-17 12:52:26 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1814238]

Comment 4 Rohit Keshri 2020-03-20 12:18:19 UTC

Mitigation:

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Comment 5 Rohit Keshri 2020-03-20 12:19:26 UTC

Statement:

The affected code was not introduced into any kernel versions shipped with Red Hat Enterprise Linux making this vulnerable not applicable to these platforms.

Comment 7 Product Security DevOps Team 2020-03-23 16:32:17 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-2020-9391