linux-cve-announce - CVE-2025-21926: net: gso: fix ownership in __udp_gso

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Message-ID: <2025040132-CVE-2025-21926-fd40@gregkh>
Date: Tue,  1 Apr 2025 16:39:50 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21926: net: gso: fix ownership in __udp_gso_segment

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:

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.

The Linux kernel CVE team has assigned CVE-2025-21926 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 5.4.291 with commit 9f28205ddb76e86cac418332e952241d85fed0dc
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 5.10.235 with commit a2d1cca955ed34873e524cc2e6e885450d262f05
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 5.15.179 with commit 455217ac9db0cf9349b3933664355e907bb1a569
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 6.1.131 with commit e8db70537878e1bb3fd83e5abcc6feefc0587828
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 6.6.83 with commit 01a83237644d6822bc7df2c5564fc81b0df84358
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 6.12.19 with commit 084819b0d8b1bd433b90142371eb9450d657f8ca
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 6.13.7 with commit c32da44cc9298eaa6109e3fc2c2b4e07cc4bf11b
	Issue introduced in 4.18 with commit ad405857b174ed31a97982bb129c320d03321cf5 and fixed in 6.14 with commit ee01b2f2d7d0010787c2343463965bbc283a497f

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21926
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/ipv4/udp_offload.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9f28205ddb76e86cac418332e952241d85fed0dc
	https://git.kernel.org/stable/c/a2d1cca955ed34873e524cc2e6e885450d262f05
	https://git.kernel.org/stable/c/455217ac9db0cf9349b3933664355e907bb1a569
	https://git.kernel.org/stable/c/e8db70537878e1bb3fd83e5abcc6feefc0587828
	https://git.kernel.org/stable/c/01a83237644d6822bc7df2c5564fc81b0df84358
	https://git.kernel.org/stable/c/084819b0d8b1bd433b90142371eb9450d657f8ca
	https://git.kernel.org/stable/c/c32da44cc9298eaa6109e3fc2c2b4e07cc4bf11b
	https://git.kernel.org/stable/c/ee01b2f2d7d0010787c2343463965bbc283a497f