CVE-2026-53014: net/sched: act_mirred: fix wrong device for mac_header_xmit check in tcf_blockcast_redir

CVE-2026-53014: net/sched: act_mirred: fix wrong device for mac_header_xmit check in tcf_blockcast_redir

[Greg Kroah-Hartman]

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

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

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

net/sched: act_mirred: fix wrong device for mac_header_xmit check in tcf_blockcast_redir

In tcf_blockcast_redir(), when iterating block ports to redirect
packets to multiple devices, the mac_header_xmit flag is queried
from the wrong device. The loop sends to dev_prev but queries
dev_is_mac_header_xmit(dev) — which is the NEXT device in the
iteration, not the one being sent to.

This causes tcf_mirred_to_dev() to make incorrect decisions about
whether to push or pull the MAC header. When the block contains
mixed device types (e.g., an ethernet veth and a tunnel device),
intermediate devices get the wrong mac_header_xmit flag, leading to
skb header corruption. In the worst case, skb_push_rcsum with an
incorrect mac_len can exhaust headroom and panic.

The last device in the loop is handled correctly (line 365-366 uses
dev_is_mac_header_xmit(dev_prev)), confirming this is a copy-paste
oversight for the intermediate devices.

Fix by using dev_prev instead of dev for the mac_header_xmit query,
consistent with the device actually being sent to.

The Linux kernel CVE team has assigned CVE-2026-53014 to this issue.


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

	Issue introduced in 6.8 with commit 42f39036cda808d3de243192a2cf5125f12f3047 and fixed in 6.12.91 with commit 8fda5174286119addd28473fb2ec5bdf521c05a8
	Issue introduced in 6.8 with commit 42f39036cda808d3de243192a2cf5125f12f3047 and fixed in 6.18.33 with commit 7db3e4e03032261b1b519341123fc30d995478ca
	Issue introduced in 6.8 with commit 42f39036cda808d3de243192a2cf5125f12f3047 and fixed in 7.0.10 with commit 4764953c4b47585eb72797b216b63a831dc0c7e6
	Issue introduced in 6.8 with commit 42f39036cda808d3de243192a2cf5125f12f3047 and fixed in 7.1 with commit 4510d140524ca7d6e772db962e013f26f09a63b1

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-2026-53014
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/sched/act_mirred.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/8fda5174286119addd28473fb2ec5bdf521c05a8
	https://git.kernel.org/stable/c/7db3e4e03032261b1b519341123fc30d995478ca
	https://git.kernel.org/stable/c/4764953c4b47585eb72797b216b63a831dc0c7e6
	https://git.kernel.org/stable/c/4510d140524ca7d6e772db962e013f26f09a63b1