linux-cve-announce - CVE-2023-53577: bpf, cpumap: Make sure kthread is running before map update returns

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Message-ID: <2025100455-CVE-2023-53577-96e9@gregkh>
Date: Sat,  4 Oct 2025 17:17:31 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53577: bpf, cpumap: Make sure kthread is running before map update returns

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

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

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

bpf, cpumap: Make sure kthread is running before map update returns

The following warning was reported when running stress-mode enabled
xdp_redirect_cpu with some RT threads:

  ------------[ cut here ]------------
  WARNING: CPU: 4 PID: 65 at kernel/bpf/cpumap.c:135
  CPU: 4 PID: 65 Comm: kworker/4:1 Not tainted 6.5.0-rc2+ #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
  Workqueue: events cpu_map_kthread_stop
  RIP: 0010:put_cpu_map_entry+0xda/0x220
  ......
  Call Trace:
   <TASK>
   ? show_regs+0x65/0x70
   ? __warn+0xa5/0x240
   ......
   ? put_cpu_map_entry+0xda/0x220
   cpu_map_kthread_stop+0x41/0x60
   process_one_work+0x6b0/0xb80
   worker_thread+0x96/0x720
   kthread+0x1a5/0x1f0
   ret_from_fork+0x3a/0x70
   ret_from_fork_asm+0x1b/0x30
   </TASK>

The root cause is the same as commit 436901649731 ("bpf: cpumap: Fix memory
leak in cpu_map_update_elem"). The kthread is stopped prematurely by
kthread_stop() in cpu_map_kthread_stop(), and kthread() doesn't call
cpu_map_kthread_run() at all but XDP program has already queued some
frames or skbs into ptr_ring. So when __cpu_map_ring_cleanup() checks
the ptr_ring, it will find it was not emptied and report a warning.

An alternative fix is to use __cpu_map_ring_cleanup() to drop these
pending frames or skbs when kthread_stop() returns -EINTR, but it may
confuse the user, because these frames or skbs have been handled
correctly by XDP program. So instead of dropping these frames or skbs,
just make sure the per-cpu kthread is running before
__cpu_map_entry_alloc() returns.

After apply the fix, the error handle for kthread_stop() will be
unnecessary because it will always return 0, so just remove it.

The Linux kernel CVE team has assigned CVE-2023-53577 to this issue.

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

	Issue introduced in 4.15 with commit 6710e1126934d8b4372b4d2f9ae1646cd3f151bf and fixed in 5.15.126 with commit b44d28b98f185d2f2348aa3c3636838c316f889e
	Issue introduced in 4.15 with commit 6710e1126934d8b4372b4d2f9ae1646cd3f151bf and fixed in 6.1.45 with commit 7a1178a3671b40746830d355836b72e47ceb2490
	Issue introduced in 4.15 with commit 6710e1126934d8b4372b4d2f9ae1646cd3f151bf and fixed in 6.4.10 with commit ecb45b852af5e88257020b88bea5ff0798d72aca
	Issue introduced in 4.15 with commit 6710e1126934d8b4372b4d2f9ae1646cd3f151bf and fixed in 6.5 with commit 640a604585aa30f93e39b17d4d6ba69fcb1e66c9

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-2023-53577
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:
	kernel/bpf/cpumap.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/b44d28b98f185d2f2348aa3c3636838c316f889e
	https://git.kernel.org/stable/c/7a1178a3671b40746830d355836b72e47ceb2490
	https://git.kernel.org/stable/c/ecb45b852af5e88257020b88bea5ff0798d72aca
	https://git.kernel.org/stable/c/640a604585aa30f93e39b17d4d6ba69fcb1e66c9