Описание
In the Linux kernel, the following vulnerability has been resolved: skbuff: fix coalescing for page_pool fragment recycling Fix a use-after-free when using page_pool with page fragments. We encountered this problem during normal RX in the hns3 driver: (1) Initially we have three descriptors in the RX queue. The first one allocates PAGE1 through page_pool, and the other two allocate one half of PAGE2 each. Page references look like this: RX_BD1 _______ PAGE1 RX_BD2 _______ PAGE2 RX_BD3 _________/ (2) Handle RX on the first descriptor. Allocate SKB1, eventually added to the receive queue by tcp_queue_rcv(). (3) Handle RX on the second descriptor. Allocate SKB2 and pass it to netif_receive_skb(): netif_receive_skb(SKB2) ip_rcv(SKB2) SKB3 = skb_clone(SKB2) SKB2 and SKB3 share a reference to PAGE2 through skb_shinfo()->dataref. The other ref to PAGE2 is still held by RX_BD3: SKB2 ---+- PAGE2 SKB3 __/ / RX_BD3 ______/ (3b) Now while handling TCP, coalesce SKB3 with SKB1: tcp_v4_rcv(SKB3) tcp_try_coalesce(to=SKB1, from=SKB3) // succeeds kfree_skb_partial(SKB3) skb_release_data(SKB3) // drops one dataref SKB1 _____ PAGE1 _ SKB2 _____ PAGE2 / RX_BD3 ________/ In skb_try_coalesce(), skb_frag_ref() takes a page reference to PAGE2, where it should instead have increased the page_pool frag reference, pp_frag_count. Without coalescing, when releasing both SKB2 and SKB3, a single reference to PAGE2 would be dropped. Now when releasing SKB1 and SKB2, two references to PAGE2 will be dropped, resulting in underflow. (3c) Drop SKB2: af_packet_rcv(SKB2) consume_skb(SKB2) skb_release_data(SKB2) // drops second dataref page_pool_return_skb_page(PAGE2) // drops one pp_frag_count SKB1 _____ PAGE1 _ PAGE2 / RX_BD3 _________/ (4) Userspace calls recvmsg() Copies SKB1 and releases it. Since SKB3 was coalesced with SKB1, we release the SKB3 page as well: tcp_eat_recv_skb(SKB1) skb_release_data(SKB1) page_pool_return_skb_page(PAGE1) page_pool_return_skb_page(PAGE2) // drops second pp_frag_count (5) PAGE2 is freed, but the third RX descriptor was still using it! In our case this causes IOMMU faults, but it would silently corrupt memory if the IOMMU was disabled. Change the logic that checks whether pp_recycle SKBs can be coalesced. We still reject differing pp_recycle between 'from' and 'to' SKBs, but in order to avoid the situation described above, we also reject coalescing when both 'from' and 'to' are pp_recycled and 'from' is cloned. The new logic allows coalescing a cloned pp_recycle SKB into a page refcounted one, because in this case the release (4) will drop the right reference, the one taken by skb_try_coalesce().
Отчет
The bug in memory management of networking that can lead to IOMMU faults or to use after free. The attack complexity is high, because few complex conditions should happen together (that hard to trigger). For the Red Hat Enterprise Linux (all versions) bug not actual, because already fixed.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2022:8267 | 15.11.2022 |
| Red Hat Enterprise Linux 9 | kernel | Fixed | RHSA-2022:8267 | 15.11.2022 |
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Дополнительная информация
Статус:
EPSS
7 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: skbuff: fix coalescing for page_pool fragment recycling Fix a use-after-free when using page_pool with page fragments. We encountered this problem during normal RX in the hns3 driver: (1) Initially we have three descriptors in the RX queue. The first one allocates PAGE1 through page_pool, and the other two allocate one half of PAGE2 each. Page references look like this: RX_BD1 _______ PAGE1 RX_BD2 _______ PAGE2 RX_BD3 _________/ (2) Handle RX on the first descriptor. Allocate SKB1, eventually added to the receive queue by tcp_queue_rcv(). (3) Handle RX on the second descriptor. Allocate SKB2 and pass it to netif_receive_skb(): netif_receive_skb(SKB2) ip_rcv(SKB2) SKB3 = skb_clone(SKB2) SKB2 and SKB3 share a reference to PAGE2 through skb_shinfo()->dataref. The other ref to PAGE2 is still held by RX_BD3: SKB2 ---+- PAGE2 SKB3 __/ / RX_BD3 _________/ (3b) Now while handling TCP, coalesce SKB3 with SKB1: tcp_v4_rcv(S...
In the Linux kernel, the following vulnerability has been resolved: skbuff: fix coalescing for page_pool fragment recycling Fix a use-after-free when using page_pool with page fragments. We encountered this problem during normal RX in the hns3 driver: (1) Initially we have three descriptors in the RX queue. The first one allocates PAGE1 through page_pool, and the other two allocate one half of PAGE2 each. Page references look like this: RX_BD1 _______ PAGE1 RX_BD2 _______ PAGE2 RX_BD3 _________/ (2) Handle RX on the first descriptor. Allocate SKB1, eventually added to the receive queue by tcp_queue_rcv(). (3) Handle RX on the second descriptor. Allocate SKB2 and pass it to netif_receive_skb(): netif_receive_skb(SKB2) ip_rcv(SKB2) SKB3 = skb_clone(SKB2) SKB2 and SKB3 share a reference to PAGE2 through skb_shinfo()->dataref. The other ref to PAGE2 is still held by RX_BD3:
In the Linux kernel, the following vulnerability has been resolved: s ...
In the Linux kernel, the following vulnerability has been resolved: skbuff: fix coalescing for page_pool fragment recycling Fix a use-after-free when using page_pool with page fragments. We encountered this problem during normal RX in the hns3 driver: (1) Initially we have three descriptors in the RX queue. The first one allocates PAGE1 through page_pool, and the other two allocate one half of PAGE2 each. Page references look like this: RX_BD1 _______ PAGE1 RX_BD2 _______ PAGE2 RX_BD3 _________/ (2) Handle RX on the first descriptor. Allocate SKB1, eventually added to the receive queue by tcp_queue_rcv(). (3) Handle RX on the second descriptor. Allocate SKB2 and pass it to netif_receive_skb(): netif_receive_skb(SKB2) ip_rcv(SKB2) SKB3 = skb_clone(SKB2) SKB2 and SKB3 share a reference to PAGE2 through skb_shinfo()->dataref. The other ref to PAGE2 is still held by RX_BD3: ...
Уязвимость функции skb_try_coalesce() модуля net/core/skbuff.c поддержки сетевых функций ядра операционной системы Linux, позволяющая нарушителю оказать воздействие на конфиденциальность, целостность и доступность защищаемой информации
EPSS
7 High
CVSS3