CVE-2024-56770

/// Technical description

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

net/sched: netem: account for backlog updates from child qdisc

In general, 'qlen' of any classful qdisc should keep track of the

number of packets that the qdisc itself and all of its children holds.

In case of netem, 'qlen' only accounts for the packets in its internal

tfifo. When netem is used with a child qdisc, the child qdisc can use

'qdisc_tree_reduce_backlog' to inform its parent, netem, about created

or dropped SKBs. This function updates 'qlen' and the backlog statistics

of netem, but netem does not account for changes made by a child qdisc.

'qlen' then indicates the wrong number of packets in the tfifo.

If a child qdisc creates new SKBs during enqueue and informs its parent

about this, netem's 'qlen' value is increased. When netem dequeues the

newly created SKBs from the child, the 'qlen' in netem is not updated.

If 'qlen' reaches the configured sch->limit, the enqueue function stops

working, even though th

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References