CVE-2024-53057

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 its 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(-)

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• 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