linux-cve-announce - CVE-2025-21640: sctp: sysctl: cookie_hmac

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Message-ID: <2025011944-CVE-2025-21640-4dd1@gregkh>
Date: Sun, 19 Jan 2025 11:17:49 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21640: sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

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

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

sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.sctp_hmac_alg' is
used.

The Linux kernel CVE team has assigned CVE-2025-21640 to this issue.


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

	Issue introduced in 3.8 with commit 3c68198e75111a905ac2412be12bf7b29099729b and fixed in 6.1.125 with commit 3cd0659deb9c03535fd61839e91d4d4d3e51ac71
	Issue introduced in 3.8 with commit 3c68198e75111a905ac2412be12bf7b29099729b and fixed in 6.6.72 with commit ad673e514b2793b8d5902f6ba6ab7e890dea23d5
	Issue introduced in 3.8 with commit 3c68198e75111a905ac2412be12bf7b29099729b and fixed in 6.12.10 with commit f0bb3935470684306e4e04793a20ac4c4b08de0b
	Issue introduced in 3.8 with commit 3c68198e75111a905ac2412be12bf7b29099729b and fixed in 6.13-rc7 with commit ea62dd1383913b5999f3d16ae99d411f41b528d4

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-2025-21640
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/sctp/sysctl.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/3cd0659deb9c03535fd61839e91d4d4d3e51ac71
	https://git.kernel.org/stable/c/ad673e514b2793b8d5902f6ba6ab7e890dea23d5
	https://git.kernel.org/stable/c/f0bb3935470684306e4e04793a20ac4c4b08de0b
	https://git.kernel.org/stable/c/ea62dd1383913b5999f3d16ae99d411f41b528d4