net: ioam6: fix OOB and missing lock

Overview

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

net: ioam6: fix OOB and missing lock

When trace->type.bit6 is set:

if (trace->type.bit6) {
    ...
    queue = skb_get_tx_queue(dev, skb);
    qdisc = rcu_dereference(queue->qdisc);

This code can lead to an out-of-bounds access of the dev->_tx[] array when is_input is true. In such a case, the packet is on the RX path and skb->queue_mapping contains the RX queue index of the ingress device. If the ingress device has more RX queues than the egress device (dev) has TX queues, skb_get_queue_mapping(skb) will exceed dev->num_tx_queues. Add a check to avoid this situation since skb_get_tx_queue() does not clamp the index. This issue has also revealed that per queue visibility cannot be accurate and will be replaced later as a new feature.

While at it, add missing lock around qdisc_qstats_qlen_backlog(). The function __ioam6_fill_trace_data() is called from both softirq and process contexts, hence the use of spin_lock_bh() here.

Affected

• Linux >= b63c5478e9cb1d1504eb02d9dac827ad24612b32 < 6d1d9ed9b409e0662241e3d245d574a18f643494
• Linux >= b63c5478e9cb1d1504eb02d9dac827ad24612b32 < 95a1334748c95dd15546056280ade0c4b8dd7b78
• Linux >= b63c5478e9cb1d1504eb02d9dac827ad24612b32 < b30b1675aa2bcf0491fd3830b051df4e08a7c8ca
• Linux 5.17

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.