Bug 1900933 (CVE-2020-27786) - CVE-2020-27786 kernel: use-after-free in kernel midi subsystem
Summary: CVE-2020-27786 kernel: use-after-free in kernel midi subsystem
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2020-27786
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Nobody
QA Contact:
URL:
Whiteboard:
Depends On: 1869536 1900948 1900949 1900950 1900951 1900952 1900953 1900954 1900955 1900956 1900957 1900958 1902539 1902540 1902541 1902542 1903894 1914738
Blocks: 1899667 1936789
TreeView+ depends on / blocked
 
Reported: 2020-11-24 03:00 UTC by Wade Mealing
Modified: 2023-07-11 08:47 UTC (History)
40 users (show)

Fixed In Version: kernel 5.7-rc6
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the Linux kernel’s implementation of MIDI, where an attacker with a local account and the permissions to issue ioctl commands to midi devices could trigger a use-after-free issue. A write to this specific memory while freed and before use causes the flow of execution to change and possibly allow for memory corruption or privilege escalation. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Clone Of:
Environment:
Last Closed: 2023-07-11 08:47:53 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2021:2538 0 None None None 2021-06-23 18:06:06 UTC
Red Hat Product Errata RHBA-2021:2541 0 None None None 2021-06-24 11:51:17 UTC

Description Wade Mealing 2020-11-24 03:00:30 UTC 
A flaw was found in the Linux kernels implementation of MIDI, where an attacker with a local account and the permissions to issue an ioctl commands to midi devices, could trigger a use-after-free.  A write to this specific memory while freed and before use could cause the flow of execution to change and possibly allow for memory corruption or privilege escalation.

This would only affect systems that have attached local MIDI hardware with the midi kernel modules loaded.
Comment 2 Wade Mealing 2020-11-24 04:41:47 UTC 
External References:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c1f6e3c818dd734c30f6a7eeebf232ba2cf3181d
Comment 4 Wade Mealing 2020-11-24 04:47:03 UTC 
Mitigation:


As the midi module will be auto-loaded when required, its use can be disabled by preventing the module from loading with the following instructions:

# echo "install snd-rawmidi /bin/true" >> /etc/modprobe.d/disable-snd-rawmidi.conf

The system will need to be restarted if the snd-rawmidi modules are loaded. In most circumstances, the CIFS kernel modules will be unable to be unloaded while any midi / sound devices are active and the protocol is in use.

If the system requires this module to work correctly, this mitigation may not be suitable.

If you need further assistance, see KCS article https://access.redhat.com/solutions/41278 or contact Red Hat Global Support Services.
Comment 8 Wade Mealing 2020-12-03 03:49:27 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1903894]
Comment 9 Justin M. Forbes 2020-12-03 13:39:59 UTC 
This was fixed for Fedora with the 5.6.14 stable kernel updates.
Comment 11 errata-xmlrpc 2021-05-18 13:20:32 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:1578 https://access.redhat.com/errata/RHSA-2021:1578
Comment 12 errata-xmlrpc 2021-05-18 14:40:54 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:1739 https://access.redhat.com/errata/RHSA-2021:1739
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