Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
net: gso: fix ownership in __udp_gso_segment
In __udp_gso_segment the skb destructor is removed before segmenting the skb but the socket reference is kept as-is. This is an issue if the original skb is later orphaned as we can hit the following bug:
kernel BUG at ./include/linux/skbuff.h:3312! (skb_orphan) RIP: 0010:ip_rcv_core+0x8b2/0xca0 Call Trace: ip_rcv+0xab/0x6e0 __netif_receive_skb_one_core+0x168/0x1b0 process_backlog+0x384/0x1100 __napi_poll.constprop.0+0xa1/0x370 net_rx_action+0x925/0xe50
The above can happen following a sequence of events when using OpenVSwitch, when an OVS_ACTION_ATTR_USERSPACE action precedes an OVS_ACTION_ATTR_OUTPUT action:
- OVS_ACTION_ATTR_USERSPACE is handled (in do_execute_actions): the skb goes through queue_gso_packets and then __udp_gso_segment, where its destructor is removed.
- The segments’ data are copied and sent to userspace.
- OVS_ACTION_ATTR_OUTPUT is handled (in do_execute_actions) and the same original skb is sent to its path.
- If it later hits skb_orphan, we hit the bug.
Fix this by also removing the reference to the socket in __udp_gso_segment.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , Oracle Linux 7 ELS , TuxCare 9.6 ESU , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- linux @ 4.15.0 (+7 more)
In the Linux kernel, the following vulnerability has been resolved:
net: gso: fix ownership in __udp_gso_segment
In __udp_gso_segment the skb destructor is removed before segmenting the skb but the socket reference is kept as-is. This is an issue if the original skb is later orphaned as we can hit the following bug:
kernel BUG at ./include/linux/skbuff.h:3312! (skb_orphan) RIP: 0010:ip_rcv_core+0x8b2/0xca0 Call Trace: ip_rcv+0xab/0x6e0 __netif_receive_skb_one_core+0x168/0x1b0 process_backlog+0x384/0x1100 __napi_poll.constprop.0+0xa1/0x370 net_rx_action+0x925/0xe50
The above can happen following a sequence of events when using OpenVSwitch, when an OVS_ACTION_ATTR_USERSPACE action precedes an OVS_ACTION_ATTR_OUTPUT action:
- OVS_ACTION_ATTR_USERSPACE is handled (in do_execute_actions): the skb goes through queue_gso_packets and then __udp_gso_segment, where its destructor is removed.
- The segments’ data are copied and sent to userspace.
- OVS_ACTION_ATTR_OUTPUT is handled (in do_execute_actions) and the same original skb is sent to its path.
- If it later hits skb_orphan, we hit the bug.
Fix this by also removing the reference to the socket in __udp_gso_segment.