CVE-2025-21926 Information

Apr 03, 2025 cve

Description

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.

Reference

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