Bug 1769670 (CVE-2017-8284) - CVE-2017-8284 QEMU: privilege escalation via disas_insn function in TCG mode
Summary: CVE-2017-8284 QEMU: privilege escalation via disas_insn function in TCG mode
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2017-8284
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1769671
Blocks: 1781081
TreeView+ depends on / blocked
 
Reported: 2019-11-07 07:17 UTC by Dhananjay Arunesh
Modified: 2020-01-07 03:03 UTC (History)
33 users (show)

Fixed In Version: QEMU 2.9.4
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2019-12-18 08:09:27 UTC


Attachments (Terms of Use)

Description Dhananjay Arunesh 2019-11-07 07:17:42 UTC
The disas_insn function in target/i386/translate.c in QEMU before 2.9.0, when TCG mode without hardware acceleration is used, does not limit the instruction size, which allows local users to gain privileges by creating a modified basic block that injects code into a setuid program, as demonstrated by procmail.

Reference:
https://github.com/qemu/qemu/commit/30663fd26c0307e414622c7a8607fbc04f92ec14
https://bugs.chromium.org/p/project-zero/issues/detail?id=1122

Comment 1 Dhananjay Arunesh 2019-11-07 07:17:55 UTC
Created qemu tracking bugs for this issue:

Affects: epel-7 [bug 1769671]

Comment 2 Daniel Berrangé 2019-12-09 10:50:43 UTC
Note that the QEMU project currently declares that any TCG bugs are NOT considered security issues as TCG emulation implementation is not considered to be of a quality that will provide guest isolation from the host:

  "The non-virtualization use case covers emulation using the Tiny Code Generator
   (TCG).  In principle the TCG and device emulation code used in conjunction with
   the non-virtualization use case should meet the same security requirements as
   the virtualization use case.  However, for historical reasons much of the
   non-virtualization use case code was not written with these security
   requirements in mind.
   
   Bugs affecting the non-virtualization use case are not considered security
   bugs at this time.  Users with non-virtualization use cases must not rely on
   QEMU to provide guest isolation or any security guarantees."

https://git.qemu.org/?p=qemu.git;a=blob;f=docs/security.texi;h=0d6b30edfc0b1582c9b55af3abb3a09dd250832b;hb=master#l37

Comment 5 Nick Tait 2019-12-16 22:11:29 UTC
Thanks for bringing that to Product Security's attention Daniel.

Comment 6 Product Security DevOps Team 2019-12-18 08:09:27 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-2017-8284


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