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.