Bug 2356587 (CVE-2025-21926)

Summary:	CVE-2025-21926 kernel: net: gso: fix ownership in __udp_gso_segment
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-04-01 16:01:14 UTC

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.

Comment 1 Robb Gatica 2025-04-02 05:46:54 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025040132-CVE-2025-21926-fd40@gregkh/T

Comment 3 errata-xmlrpc 2025-06-09 07:19:48 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2025:8643 https://access.redhat.com/errata/RHSA-2025:8643

Comment 4 errata-xmlrpc 2025-06-09 12:55:39 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2025:8669 https://access.redhat.com/errata/RHSA-2025:8669