linux-cve-announce - CVE-2025-21726: padata: avoid UAF for reorder

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Message-ID: <2025022648-CVE-2025-21726-73b1@gregkh>
Date: Wed, 26 Feb 2025 18:06:21 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21726: padata: avoid UAF for reorder_work

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

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

padata: avoid UAF for reorder_work

Although the previous patch can avoid ps and ps UAF for _do_serial, it
can not avoid potential UAF issue for reorder_work. This issue can
happen just as below:

crypto_request			crypto_request		crypto_del_alg
padata_do_serial
  ...
  padata_reorder
    // processes all remaining
    // requests then breaks
    while (1) {
      if (!padata)
        break;
      ...
    }

				padata_do_serial
				  // new request added
				  list_add
    // sees the new request
    queue_work(reorder_work)
				  padata_reorder
				    queue_work_on(squeue->work)
...

				<kworker context>
				padata_serial_worker
				// completes new request,
				// no more outstanding
				// requests

							crypto_del_alg
							  // free pd

<kworker context>
invoke_padata_reorder
  // UAF of pd

To avoid UAF for 'reorder_work', get 'pd' ref before put 'reorder_work'
into the 'serial_wq' and put 'pd' ref until the 'serial_wq' finish.

The Linux kernel CVE team has assigned CVE-2025-21726 to this issue.


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

	Issue introduced in 5.6 with commit bbefa1dd6a6d53537c11624752219e39959d04fb and fixed in 6.1.129 with commit 7000507bb0d2ceb545c0a690e0c707c897d102c2
	Issue introduced in 5.6 with commit bbefa1dd6a6d53537c11624752219e39959d04fb and fixed in 6.6.76 with commit 6f45ef616775b0ce7889b0f6077fc8d681ab30bc
	Issue introduced in 5.6 with commit bbefa1dd6a6d53537c11624752219e39959d04fb and fixed in 6.12.13 with commit 8ca38d0ca8c3d30dd18d311f1a7ec5cb56972cac
	Issue introduced in 5.6 with commit bbefa1dd6a6d53537c11624752219e39959d04fb and fixed in 6.13.2 with commit a54091c24220a4cd847d5b4f36d678edacddbaf0
	Issue introduced in 5.6 with commit bbefa1dd6a6d53537c11624752219e39959d04fb and fixed in 6.14-rc1 with commit dd7d37ccf6b11f3d95e797ebe4e9e886d0332600
	Issue introduced in 5.4.19 with commit b4c8ed0bf977760a206997b6429a7ac91978f440
	Issue introduced in 5.5.3 with commit e43d65719527043f1ef79ecba9d4ede58cbc7ffe

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-2025-21726
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/padata.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/7000507bb0d2ceb545c0a690e0c707c897d102c2
	https://git.kernel.org/stable/c/6f45ef616775b0ce7889b0f6077fc8d681ab30bc
	https://git.kernel.org/stable/c/8ca38d0ca8c3d30dd18d311f1a7ec5cb56972cac
	https://git.kernel.org/stable/c/a54091c24220a4cd847d5b4f36d678edacddbaf0
	https://git.kernel.org/stable/c/dd7d37ccf6b11f3d95e797ebe4e9e886d0332600