CVE-2025-21926

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:

1. 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.
2. The segments data are copied and sent to userspace.
3. OVS_ACTION_ATTR_OUTPUT is handled (in do_execute_actions) and the same original skb is sent to its path.
4. If it later hits skb_orphan, we hit the bug.

Fix this by also removing the reference to the socket in __udp_gso_segment.

Affected Software

References

• https://git.kernel.org/stable/c/01a83237644d6822bc7df2c5564fc81b0df84358
• https://git.kernel.org/stable/c/084819b0d8b1bd433b90142371eb9450d657f8ca
• https://git.kernel.org/stable/c/455217ac9db0cf9349b3933664355e907bb1a569
• https://git.kernel.org/stable/c/9f28205ddb76e86cac418332e952241d85fed0dc
• https://git.kernel.org/stable/c/a2d1cca955ed34873e524cc2e6e885450d262f05
• https://git.kernel.org/stable/c/c32da44cc9298eaa6109e3fc2c2b4e07cc4bf11b
• https://git.kernel.org/stable/c/e8db70537878e1bb3fd83e5abcc6feefc0587828
• https://git.kernel.org/stable/c/ee01b2f2d7d0010787c2343463965bbc283a497f