CVE-2024-53057net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT

Official description

In the Linux kernel, the following vulnerability has been resolved: net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT In qdisc_tree_reduce_backlog, Qdiscs with major handle ffff: are assumed to be either root or ingress. This assumption is bogus since it's valid to create egress qdiscs with major handle ffff: Budimir Markovic found that for qdiscs like DRR that maintain an active class list, it will cause a UAF with a dangling class pointer. In 066a3b5b2346, the concern was to avoid iterating over the ingress qdisc since its parent is itself. The proper fix is to stop when parent TC_H_ROOT is reached because the only way to retrieve ingress is when a hierarchy which does not contain a ffff: major handle call into qdisc_lookup with TC_H_MAJ(TC_H_ROOT). In the scenario where major ffff: is an egress qdisc in any of the tree levels, the updates will also propagate to TC_H_ROOT, which then the iteration must stop. net/sched/sch_api.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e7f9a6f97eb067599a74f3bcb6761976b0ed303e
• https://git.kernel.org/stable/c/dbe778b08b5101df9e89bc06e0a3a7ecd2f4ef20
• https://git.kernel.org/stable/c/ce691c814bc7a3c30c220ffb5b7422715458fd9b
• https://git.kernel.org/stable/c/05df1b1dff8f197f1c275b57ccb2ca33021df552
• https://git.kernel.org/stable/c/580b3189c1972aff0f993837567d36392e9d981b
• https://git.kernel.org/stable/c/597cf9748c3477bf61bc35f0634129f56764ad24
• https://git.kernel.org/stable/c/9995909615c3431a5304c1210face5f268d24dba
• https://git.kernel.org/stable/c/2e95c4384438adeaa772caa560244b1a2efef816
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
• https://cert-portal.siemens.com/productcert/html/ssa-398330.html
• https://cert-portal.siemens.com/productcert/html/ssa-265688.html
• https://cert-portal.siemens.com/productcert/html/ssa-355557.html