CVE-2026-64116: ipv6: ioam: add NULL check for idev in ipv6_hop_ioam()

CVE-2026-64116: ipv6: ioam: add NULL check for idev in ipv6_hop_ioam()

[Greg Kroah-Hartman]

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

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

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

ipv6: ioam: add NULL check for idev in ipv6_hop_ioam()

Reported by Sashiko:

The function ipv6_hop_ioam() accesses
__in6_dev_get(skb->dev)->cnf.ioam6_enabled without validating the returned
idev pointer. Because addrconf_ifdown() can concurrently clear dev->ip6_ptr
via RCU, __in6_dev_get() can return NULL during interface teardown, which
could cause a NULL pointer dereference when processing an IOAM Hop-by-Hop
option.

Let's add a check and use SKB_DROP_REASON_IPV6DISABLED accordingly.

The Linux kernel CVE team has assigned CVE-2026-64116 to this issue.


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

	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 5.15.210 with commit c7e8971abd70e9d022f1c251ba2508f8dc7f2db8
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 6.1.176 with commit 09cbfd4b81ae90963dadb1de99b63b702e73290a
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 6.6.143 with commit 1dca7e491f070ac49b3d934f16ee953a53b37f38
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 6.12.92 with commit 902daac307eb7e1955ce05b071950f3cba88c963
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 6.18.34 with commit abdd03229414b5a52943b65a60f34b84cea5ac59
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 7.0.11 with commit cf75eb6617042c8cff6112daeed7791809fc9dd2
	Issue introduced in 5.15 with commit 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 and fixed in 7.1 with commit d4ea0dfd75011b78cebf3808f98ac4c4f51a6fb9

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-2026-64116
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/ipv6/exthdrs.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/c7e8971abd70e9d022f1c251ba2508f8dc7f2db8
	https://git.kernel.org/stable/c/09cbfd4b81ae90963dadb1de99b63b702e73290a
	https://git.kernel.org/stable/c/1dca7e491f070ac49b3d934f16ee953a53b37f38
	https://git.kernel.org/stable/c/902daac307eb7e1955ce05b071950f3cba88c963
	https://git.kernel.org/stable/c/abdd03229414b5a52943b65a60f34b84cea5ac59
	https://git.kernel.org/stable/c/cf75eb6617042c8cff6112daeed7791809fc9dd2
	https://git.kernel.org/stable/c/d4ea0dfd75011b78cebf3808f98ac4c4f51a6fb9