In the Linux kernel, the following vulnerability has been resolved: net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs When shrinking the number of real tx queues, netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush qdiscs for queues which will no longer be used. qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with qdisc_lock(). However, for lockless qdiscs, the dequeue path is serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so qdisc_reset() can run concurrently with __qdisc_run() and free skbs while they are still being dequeued, leading to UAF. This can easily be reproduced on e.g. virtio-net by imposing heavy traffic while frequently changing the number of queue pairs: iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done With KASAN enabled, this leads to reports like: BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760 ... Call Trace: <TASK> ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ... </TASK> Allocated by task 1270 on cpu 5 at 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ... Freed by task 1306 on cpu 3 at 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ... Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the serialization model already used by dev_reset_queue(). Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state reflects an empty queue, avoiding needless re-scheduling.
En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: sched: evitar la condición de carrera entre qdisc_reset_all_tx_gt() y la eliminación de la cola para qdiscs sin bloqueo Al reducir el número de colas de transmisión (tx) reales, netif_set_real_num_tx_queues() llama a qdisc_reset_all_tx_gt() para vaciar los qdiscs de las colas que ya no se utilizarán. Actualmente, qdisc_reset_all_tx_gt() serializa qdisc_reset() con qdisc_lock(). Sin embargo, para los qdiscs sin bloqueo, la ruta de eliminación de la cola se serializa mediante qdisc_run_begin/end() usando qdisc->seqlock en su lugar, por lo que qdisc_reset() puede ejecutarse concurrentemente con __qdisc_run() y liberar skbs mientras aún se están eliminando de la cola, lo que lleva a un uso después de liberación. Esto se puede reproducir fácilmente, por ejemplo, en virtio-net, imponiendo un tráfico intenso mientras se cambia frecuentemente el número de pares de colas: iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done Con KASAN habilitado, esto lleva a informes como: BUG: KASAN: uso después de liberación de slab en __qdisc_run+0x133f/0x1760 ... Rastro de Llamada: ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ... Asignado por la tarea 1270 en la cpu 5 a los 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ... Liberado por la tarea 1306 en la cpu 3 a los 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ... Serializar qdisc_reset_all_tx_gt() contra la ruta de eliminación de la cola sin bloqueo tomando qdisc->seqlock para los qdiscs TCQ_F_NOLOCK, coincidiendo con el modelo de serialización ya utilizado por dev_reset_queue(). Además, borrar QDISC_STATE_NON_EMPTY después del reinicio para que el estado del qdisc refleje una cola vacía, evitando una reprogramación innecesaria.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
| Attack Vector | LOCAL |
|---|---|
| Attack Complexity | LOW |
| Privileges Required | LOW |
| User Interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality Impact | HIGH |
| Integrity Impact | HIGH |
| Availability Impact | HIGH |
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Type: Secondary
Exploitability Score: 1.8
Impact Score: 5.9
| Source | Type | Description |
|---|---|---|
| [email protected] | Primary |
en
CWE-416
|
| Vendor | Product | Version | Update | Type |
|---|---|---|---|---|
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bdc6a4740> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bdc6a7440> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702ba414df00> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bdc6a7500> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bdc6a4140> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x702bdc6a5a80> | Operating System |
| linux | linux_kernel | 4.16 | <built-in method update of dict object at 0x702b80611b40> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702bdc6a7380> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702b80610f80> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702bdc6a4640> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702ba414f880> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702bdc6a6640> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702ba414f980> | Operating System |
| linux | linux_kernel | 7.0 | <built-in method update of dict object at 0x702ba414f000> | Operating System |
| Vulnerable | CPE |
|---|---|
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:4.16:-:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* |