CVE-2021-47396

Source
https://nvd.nist.gov/vuln/detail/CVE-2021-47396
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47396.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2021-47396
Related
Published
2024-05-21T15:15:24Z
Modified
2024-09-18T03:17:27.084765Z
Summary
[none]
Details

In the Linux kernel, the following vulnerability has been resolved:

mac80211-hwsim: fix late beacon hrtimer handling

Thomas explained in https://lore.kernel.org/r/87mtoeb4hb.ffs@tglx that our handling of the hrtimer here is wrong: If the timer fires late (e.g. due to vCPU scheduling, as reported by Dmitry/syzbot) then it tries to actually rearm the timer at the next deadline, which might be in the past already:

1 2 3 N N+1 | | | ... | |

^ intended to fire here (1) ^ next deadline here (2) ^ actually fired here

The next time it fires, it's later, but will still try to schedule for the next deadline (now 3), etc. until it catches up with N, but that might take a long time, causing stalls etc.

Now, all of this is simulation, so we just have to fix it, but note that the behaviour is wrong even per spec, since there's no value then in sending all those beacons unaligned - they should be aligned to the TBTT (1, 2, 3, ... in the picture), and if we're a bit (or a lot) late, then just resume at that point.

Therefore, change the code to use hrtimerforwardnow() which will ensure that the next firing of the timer would be at N+1 (in the picture), i.e. the next interval point after the current time.

References

Affected packages

Debian:11 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
5.10.84-1

Affected versions

5.*

5.10.46-4
5.10.46-5
5.10.70-1~bpo10+1
5.10.70-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:12 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
5.14.12-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:13 / linux

Package

Name
linux
Purl
pkg:deb/debian/linux?arch=source

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
5.14.12-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}