linux-cve-announce - CVE-2025-37920: xsk: Fix race condition in AF

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Message-ID: <2025052002-CVE-2025-37920-304d@gregkh>
Date: Tue, 20 May 2025 17:22:17 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37920: xsk: Fix race condition in AF_XDP generic RX path

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

xsk: Fix race condition in AF_XDP generic RX path

Move rx_lock from xsk_socket to xsk_buff_pool.
Fix synchronization for shared umem mode in
generic RX path where multiple sockets share
single xsk_buff_pool.

RX queue is exclusive to xsk_socket, while FILL
queue can be shared between multiple sockets.
This could result in race condition where two
CPU cores access RX path of two different sockets
sharing the same umem.

Protect both queues by acquiring spinlock in shared
xsk_buff_pool.

Lock contention may be minimized in the future by some
per-thread FQ buffering.

It's safe and necessary to move spin_lock_bh(rx_lock)
after xsk_rcv_check():
* xs->pool and spinlock_init is synchronized by
  xsk_bind() -> xsk_is_bound() memory barriers.
* xsk_rcv_check() may return true at the moment
  of xsk_release() or xsk_unbind_dev(),
  however this will not cause any data races or
  race conditions. xsk_unbind_dev() removes xdp
  socket from all maps and waits for completion
  of all outstanding rx operations. Packets in
  RX path will either complete safely or drop.

The Linux kernel CVE team has assigned CVE-2025-37920 to this issue.

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

	Issue introduced in 5.3 with commit bf0bdd1343efbbf65b4d53aef1fce14acbd79d50 and fixed in 6.12.28 with commit 65d3c570614b892257dc58a1b202908242ecf8fd
	Issue introduced in 5.3 with commit bf0bdd1343efbbf65b4d53aef1fce14acbd79d50 and fixed in 6.14.6 with commit 75a240a3e8abf17b9e00b0ef0492b1bbaa932251
	Issue introduced in 5.3 with commit bf0bdd1343efbbf65b4d53aef1fce14acbd79d50 and fixed in 6.15-rc5 with commit a1356ac7749cafc4e27aa62c0c4604b5dca4983e
	Issue introduced in 5.1.20 with commit fd7c22ba7a0ad898b9ecf77dd53f5ccc48492e35
	Issue introduced in 5.2.3 with commit 8a090e3b73eaffe18e08ccc3fb5abecf6b0a9781

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-2025-37920
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:
	include/net/xdp_sock.h
	include/net/xsk_buff_pool.h
	net/xdp/xsk.c
	net/xdp/xsk_buff_pool.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/65d3c570614b892257dc58a1b202908242ecf8fd
	https://git.kernel.org/stable/c/75a240a3e8abf17b9e00b0ef0492b1bbaa932251
	https://git.kernel.org/stable/c/a1356ac7749cafc4e27aa62c0c4604b5dca4983e