Bug#1023656: snmpd crashes while processing network interfaces

[Stephan Peijnik-Steinwender]

Package: snmpd
Version: 5.9+dfsg-4+deb11u1
Severity: important

Dear Maintainer,

We have come across multiple situations in which snmpd would seemingly randomly
crash on a large number of production systems, whereas only Debian 11 is
affected.

The root cause of this seems to be a race condition that is triggered when a
network interface disappears during its processing.
While this case may sound unlikely we have seen frequent crashes on systems
running (short-lived) docker containers, which get veth network interfaces
added and removed in short time frames.

It turns out that this issue is known upstream ([0]) and fixed in 5.9.3 as
available from Debian testing.
A backport of net-snmp 5.9.3 to bullseye without any further adjustments fixed
the issue for us and we have since been unable to reproduce the issue.


-- System Information:
Debian Release: 11.5
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500,
'stable')
Architecture: amd64 (x86_64)

[0] https://github.com/net-snmp/net-snmp/issues/107