Use After Free Affecting kernel-tools package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-tools package and not the kernel-tools package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

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(-)

• https://access.redhat.com/security/cve/CVE-2024-53057
• https://git.kernel.org/stable/c/05df1b1dff8f197f1c275b57ccb2ca33021df552
• https://git.kernel.org/stable/c/2e95c4384438adeaa772caa560244b1a2efef816
• 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/ce691c814bc7a3c30c220ffb5b7422715458fd9b
• https://git.kernel.org/stable/c/dbe778b08b5101df9e89bc06e0a3a7ecd2f4ef20
• https://git.kernel.org/stable/c/e7f9a6f97eb067599a74f3bcb6761976b0ed303e