Описание
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: check device type before reading ETH_ADDRS __skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb) when FLOW_DISSECTOR_KEY_ETH_ADDRS is requested. This assumes the skb has a valid Ethernet header at mac_header, which is not always the case. The problem can be triggered by:
- Creating a TUN device in L3 mode (IFF_TUN, hard_header_len=0)
- Attaching a multiq qdisc with a flower filter matching on eth_src
- Sending a packet through AF_PACKET
Since TUN in L3 mode has no link-layer header, mac_header points to
the L3 data area. The flow dissector reads 12 bytes of uninitialized
skb memory, which then propagates through fl_set_masked_key() and is
used as a rhashtable lookup key in __fl_lookup(), as reported by KMSAN.
Rejecting the filter in the control path (at tc filter add time) is
not feasible because TC filter blocks can be shared between arbitrary
devices -- a filter installed on an Ethernet device may later classify
packets on a headerless device through a shared block. The device
association is not fixed at filter creation time.
Fix this by gating the memcpy on dev->type == ARPHRD_ETHER, which
ensures only true Ethernet-framed packets have their addresses read.
This is more precise than the previous hard_header_len >= 12 check,
which would incorrectly pass for non-Ethernet link types like IPoIB
(ARPHRD_INFINIBAND, hard_header_len=24) and FDDI (hard_header_len=21)
whose L2 headers are not in Ethernet format. Additionally check
skb_mac_header_was_set() to guard against the pathological case where
mac_header is the unset sentinel (~0U), which would cause eth_hdr() to
return a wild pointer.
For the act_mirred redirect case (Ethernet packet redirected to a
non-Ethernet device sharing a TC block), zeroing the key is the correct
behavior: the packet is now being classified on the target device, where
Ethernet address matching is not semantically meaningful.
Note: on non-Ethernet devices, the zeroed key will match a filter
configured with all-zero MAC addresses. This is an improvement over the
previous behavior where uninitialized memory could randomly match any
filter.
A flaw was found in the Linux kernel's flow_dissector component. When processing network packets on non-Ethernet devices, such as a TUN device in L3 mode, with specific traffic control filters, the flow_dissector can attempt to read Ethernet header information that does not exist. This leads to the use of uninitialized kernel memory as a lookup key, which could result in information disclosure or unexpected packet matching behavior.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred |
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Дополнительная информация
Статус:
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: check device type before reading ETH_ADDRS __skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb) when FLOW_DISSECTOR_KEY_ETH_ADDRS is requested. This assumes the skb has a valid Ethernet header at mac_header, which is not always the case. The problem can be triggered by: 1. Creating a TUN device in L3 mode (IFF_TUN, hard_header_len=0) 2. Attaching a multiq qdisc with a flower filter matching on eth_src 3. Sending a packet through AF_PACKET Since TUN in L3 mode has no link-layer header, mac_header points to the L3 data area. The flow dissector reads 12 bytes of uninitialized skb memory, which then propagates through fl_set_masked_key() and is used as a rhashtable lookup key in __fl_lookup(), as reported by KMSAN. Rejecting the filter in the control path (at tc filter add time) is not feasible because TC filter blocks can be shared between arbitrary devices -- a filter installed on an E...
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: check device type before reading ETH_ADDRS __skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb) when FLOW_DISSECTOR_KEY_ETH_ADDRS is requested. This assumes the skb has a valid Ethernet header at mac_header, which is not always the case. The problem can be triggered by: 1. Creating a TUN device in L3 mode (IFF_TUN, hard_header_len=0) 2. Attaching a multiq qdisc with a flower filter matching on eth_src 3. Sending a packet through AF_PACKET Since TUN in L3 mode has no link-layer header, mac_header points to the L3 data area. The flow dissector reads 12 bytes of uninitialized skb memory, which then propagates through fl_set_masked_key() and is used as a rhashtable lookup key in __fl_lookup(), as reported by KMSAN. Rejecting the filter in the control path (at tc filter add time) is not feasible because TC filter blocks can be shared between arbitrary devices -- a filter installed on
In the Linux kernel, the following vulnerability has been resolved: f ...
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: check device type before reading ETH_ADDRS __skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb) when FLOW_DISSECTOR_KEY_ETH_ADDRS is requested. This assumes the skb has a valid Ethernet header at mac_header, which is not always the case. The problem can be triggered by: 1. Creating a TUN device in L3 mode (IFF_TUN, hard_header_len=0) 2. Attaching a multiq qdisc with a flower filter matching on eth_src 3. Sending a packet through AF_PACKET Since TUN in L3 mode has no link-layer header, mac_header points to the L3 data area. The flow dissector reads 12 bytes of uninitialized skb memory, which then propagates through fl_set_masked_key() and is used as a rhashtable lookup key in __fl_lookup(), as reported by KMSAN. Rejecting the filter in the control path (at tc filter add time) is not feasible because TC filter blocks can be shared between arbitrary devices -- a filter installed...
5.5 Medium
CVSS3