CVE-2026-98569: ip_gre: Reject enabling collect metadata through changelink

CVE-2026-98569: ip_gre: Reject enabling collect metadata through changelink

[Greg Kroah-Hartman]

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

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

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

ip_gre: Reject enabling collect metadata through changelink

ipgre_netlink_parms() can enable collect_md on an existing GRE, GRETAP
or ERSPAN device. Unlike newlink, changelink does not enforce metadata
tunnel uniqueness. Converting a non-metadata device can therefore
replace the metadata receive entry for another device of the same type
in the same netns. Deleting either device then clears the shared entry,
breaking metadata receive lookup for the surviving device.

If parameter validation fails after collect_md is set, deleting the
modified device can also clear an entry it never owned.

Reject enabling metadata mode in both changelink callbacks before any
encapsulation or tunnel parameters are modified. Allow requests that
repeat the metadata attribute on an existing metadata device.

The Linux kernel CVE team has assigned CVE-2026-98569 to this issue.


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

	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 5.10.271 with commit c80315da84998b69b8829785a174b0bf72a81992
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 5.15.222 with commit cff8b520312e750ad38967c30128e1534cbf9484
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 6.1.189 with commit 1dc759571f3df14891175fc52527f7624ba01322
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 6.6.158 with commit da2e0cfbb620b199927a1e5b93b7cfde32083c7d
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 6.12.112 with commit 2e54d53b65e296b4b4bdc2cdd3b2b58dfa8d8c5c
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 6.18.55 with commit bdd41b96e814300c66222cf4e47ecb8aef995656
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 7.2.9 with commit 63c5e48d6f7f5722a48f63e13e961dc5302894ed
	Issue introduced in 4.3 with commit 2e15ea390e6f4466655066d97e22ec66870a042c and fixed in 7.3-rc5 with commit a3f315be9d30eeb6938d11fa17fd4b32d52f7c42

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-2026-98569
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/ipv4/ip_gre.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/c80315da84998b69b8829785a174b0bf72a81992
	https://git.kernel.org/stable/c/cff8b520312e750ad38967c30128e1534cbf9484
	https://git.kernel.org/stable/c/1dc759571f3df14891175fc52527f7624ba01322
	https://git.kernel.org/stable/c/da2e0cfbb620b199927a1e5b93b7cfde32083c7d
	https://git.kernel.org/stable/c/2e54d53b65e296b4b4bdc2cdd3b2b58dfa8d8c5c
	https://git.kernel.org/stable/c/bdd41b96e814300c66222cf4e47ecb8aef995656
	https://git.kernel.org/stable/c/63c5e48d6f7f5722a48f63e13e961dc5302894ed
	https://git.kernel.org/stable/c/a3f315be9d30eeb6938d11fa17fd4b32d52f7c42