Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop
In cake_drop(), qdisc_tree_reduce_backlog() is used to update the qlen and backlog of the qdisc hierarchy. Its caller, cake_enqueue(), assumes that the parent qdisc will enqueue the current packet. However, this assumption breaks when cake_enqueue() returns NET_XMIT_CN: the parent qdisc stops enqueuing current packet, leaving the tree qlen/backlog accounting inconsistent. This mismatch can lead to a NULL dereference (e.g., when the parent Qdisc is qfq_qdisc).
This patch computes the qlen/backlog delta in a more robust way by observing the difference before and after the series of cake_drop() calls, and then compensates the qdisc tree accounting if cake_enqueue() returns NET_XMIT_CN.
To ensure correct compensation when ACK thinning is enabled, a new variable is introduced to keep qlen unchanged.
Details
- Affected product:
- AlmaLinux 9.2 ESU , Ubuntu 20.04 ELS
- Affected packages:
- kernel @ 5.14.0 (+1 more)
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| AlmaLinux 9 | Released |
97 kernels
|
| Amazon Linux 2023 | Planned | — |
| Debian 11 | Will Not Fix | — |
| Debian 11 cloud | Will Not Fix | — |
| Debian 12 | Planned | — |
| Debian 13 | Will Not Fix | — |
| Oracle Linux 8 UEK 7 | Planned | — |
| Oracle Linux 9 UEK 7 | Planned | — |
| RHEL 9 | Released |
99 kernels
|
| Rocky Linux 9 | Released |
82 kernels
|
| Ubuntu 22.04 | Planned | — |
| Ubuntu 22.04 AWS | Planned | — |
| Ubuntu 24.04 | Planned | — |
| Ubuntu 24.04 AWS | Planned | — |