cve/published/2024/CVE-2024-58057.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2024-58057: idpf: convert workqueues to unbound

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

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

idpf: convert workqueues to unbound

When a workqueue is created with `WQ_UNBOUND`, its work items are
served by special worker-pools, whose host workers are not bound to
any specific CPU. In the default configuration (i.e. when
`queue_delayed_work` and friends do not specify which CPU to run the
work item on), `WQ_UNBOUND` allows the work item to be executed on any
CPU in the same node of the CPU it was enqueued on. While this
solution potentially sacrifices locality, it avoids contention with
other processes that might dominate the CPU time of the processor the
work item was scheduled on.

This is not just a theoretical problem: in a particular scenario
misconfigured process was hogging most of the time from CPU0, leaving
less than 0.5% of its CPU time to the kworker. The IDPF workqueues
that were using the kworker on CPU0 suffered large completion delays
as a result, causing performance degradation, timeouts and eventual
system crash.


* I have also run a manual test to gauge the performance
  improvement. The test consists of an antagonist process
  (`./stress --cpu 2`) consuming as much of CPU 0 as possible. This
  process is run under `taskset 01` to bind it to CPU0, and its
  priority is changed with `chrt -pQ 9900 10000 ${pid}` and
  `renice -n -20 ${pid}` after start.

  Then, the IDPF driver is forced to prefer CPU0 by editing all calls
  to `queue_delayed_work`, `mod_delayed_work`, etc... to use CPU 0.

  Finally, `ktraces` for the workqueue events are collected.

  Without the current patch, the antagonist process can force
  arbitrary delays between `workqueue_queue_work` and
  `workqueue_execute_start`, that in my tests were as high as
  `30ms`. With the current patch applied, the workqueue can be
  migrated to another unloaded CPU in the same node, and, keeping
  everything else equal, the maximum delay I could see was `6us`.

The Linux kernel CVE team has assigned CVE-2024-58057 to this issue.


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

	Issue introduced in 6.7 with commit 0fe45467a1041ea3657a7fa3a791c84c104fbd34 and fixed in 6.12.13 with commit 66bf9b3d9e1658333741f075320dc8e7cd6f8d09
	Issue introduced in 6.7 with commit 0fe45467a1041ea3657a7fa3a791c84c104fbd34 and fixed in 6.13.2 with commit 868202ec3854e13de1164e4a3e25521194c5af72
	Issue introduced in 6.7 with commit 0fe45467a1041ea3657a7fa3a791c84c104fbd34 and fixed in 6.14 with commit 9a5b021cb8186f1854bac2812bd4f396bb1e881c

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-2024-58057
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:
	drivers/net/ethernet/intel/idpf/idpf_main.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/66bf9b3d9e1658333741f075320dc8e7cd6f8d09
	https://git.kernel.org/stable/c/868202ec3854e13de1164e4a3e25521194c5af72
	https://git.kernel.org/stable/c/9a5b021cb8186f1854bac2812bd4f396bb1e881c