Bug 2031199 (CVE-2021-28714, CVE-2021-28715, XSA-392)

Summary: CVE-2021-28714 CVE-2021-28715 xen: guest can force Linux netback driver to hog large amounts of kernel memory
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED UPSTREAM QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: jforbes, m.a.young, security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2021-12-20 14:50:00 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: 2034260    
Bug Blocks:    

Description Guilherme de Almeida Suckevicz 2021-12-10 18:33:31 UTC 
Incoming data packets for a guest in the Linux kernel's netback driver are buffered until the guest is ready to process them. There are some measures taken for avoiding to pile up too much data, but those can be bypassed by the guest:

There is a timeout how long the client side of an interface can stop consuming new packets before it is assumed to have stalled, but this timeout is rather long (60 seconds by default). Using a UDP connection on a fast interface can easily accumulate gigabytes of data in that time. (CVE-2021-28715)

The timeout could even never trigger if the guest manages to have only one free slot in its RX queue ring page and the next package would require more than one free slot, which may be the case when using GSO, XDP, or software hashing. (CVE-2021-28714)

Reference:
https://xenbits.xen.org/xsa/advisory-392.html
Comment 1 Guilherme de Almeida Suckevicz 2021-12-20 14:15:23 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 2034260]
Comment 2 Product Security DevOps Team 2021-12-20 14:49:59 UTC 
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.