Bug 1905669 (CVE-2020-29566) - CVE-2020-29566 xen: undue recursion in x86 HVM context switch code (XSA-348)
Summary: CVE-2020-29566 xen: undue recursion in x86 HVM context switch code (XSA-348)
Keywords:
Status: CLOSED UPSTREAM
Alias: CVE-2020-29566
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1908085
Blocks: 1903644
TreeView+ depends on / blocked
 
Reported: 2020-12-08 19:22 UTC by Guilherme de Almeida Suckevicz
Modified: 2021-02-16 18:45 UTC (History)
4 users (show)

Fixed In Version:
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Last Closed: 2020-12-15 22:20:06 UTC


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Description Guilherme de Almeida Suckevicz 2020-12-08 19:22:27 UTC
When they require assistance from the device model, x86 HVM guests
must be temporarily de-scheduled.  The device model will signal Xen
when it has completed its operation, via an event channel, so that the
relevant vCPU is rescheduled.

If the device model were to signal Xen without having actually
completed the operation, the de-schedule / re-schedule cycle would
repeat.  If, in addition, Xen is resignalled very quickly, the
re-schedule may occur before the de-schedule was fully complete,
triggering a shortcut.  This potentially repeating process uses
ordinary recursive function calls, so could result a stack overflow.

Comment 1 Guilherme de Almeida Suckevicz 2020-12-15 19:57:47 UTC
External References:

https://www.openwall.com/lists/oss-security/2020/12/15/8

Comment 2 Guilherme de Almeida Suckevicz 2020-12-15 19:58:03 UTC
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 1908085]

Comment 3 Product Security DevOps Team 2020-12-15 22:20:06 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.


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