linux-cve-announce - CVE-2025-21639: sctp: sysctl: rto_min/max: avoid using current->nsproxy

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Message-ID: <2025011944-CVE-2025-21639-f1ca@gregkh>
Date: Sun, 19 Jan 2025 11:17:48 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21639: sctp: sysctl: rto_min/max: avoid using current->nsproxy

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

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

sctp: sysctl: rto_min/max: 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.rto_min/max' is used.

The Linux kernel CVE team has assigned CVE-2025-21639 to this issue.


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

	Issue introduced in 3.13 with commit 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 and fixed in 6.1.125 with commit 4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482
	Issue introduced in 3.13 with commit 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 and fixed in 6.6.72 with commit dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f
	Issue introduced in 3.13 with commit 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 and fixed in 6.12.10 with commit c87f1f6ade56c711f8736901e330685b453e420e
	Issue introduced in 3.13 with commit 4f3fdf3bc59cafd14c3bc2c2369efad34c7aa8b5 and fixed in 6.13-rc7 with commit 9fc17b76fc70763780aa78b38fcf4742384044a5

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-2025-21639
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/4059507e34aa5fe0fa9fd5b2b5f0c8b26ab2d482
	https://git.kernel.org/stable/c/dc9d0e3cfd16f66fbf0862857c6b391c8613ca9f
	https://git.kernel.org/stable/c/c87f1f6ade56c711f8736901e330685b453e420e
	https://git.kernel.org/stable/c/9fc17b76fc70763780aa78b38fcf4742384044a5