From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-43421: usb: gadget: f_ncm: Fix net_device lifecycle with device_move
Date: Fri, 8 May 2026 16:22:30 +0200 [thread overview]
Message-ID: <2026050847-CVE-2026-43421-82b4@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_ncm: Fix net_device lifecycle with device_move
The network device outlived its parent gadget device during
disconnection, resulting in dangling sysfs links and null pointer
dereference problems.
A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1]
was reverted due to power management ordering concerns and a NO-CARRIER
regression.
A subsequent attempt to defer net_device allocation to bind [2] broke
1:1 mapping between function instance and network device, making it
impossible for configfs to report the resolved interface name. This
results in a regression where the DHCP server fails on pmOS.
Use device_move to reparent the net_device between the gadget device and
/sys/devices/virtual/ across bind/unbind cycles. This preserves the
network interface across USB reconnection, allowing the DHCP server to
retain their binding.
Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use
__free(detach_gadget) macro to undo attachment on bind failure. The
bind_count ensures device_move executes only on the first bind.
[1] https://lore.kernel.org/lkml/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/
[2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/
The Linux kernel CVE team has assigned CVE-2026-43421 to this issue.
Affected and fixed versions
===========================
Issue introduced in 3.11 with commit 40d133d7f542616cf9538508a372306e626a16e9 and fixed in 6.12.78 with commit 93f116c3393a22acab96ad1bef12b2572eb80ca4
Issue introduced in 3.11 with commit 40d133d7f542616cf9538508a372306e626a16e9 and fixed in 6.18.19 with commit e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d
Issue introduced in 3.11 with commit 40d133d7f542616cf9538508a372306e626a16e9 and fixed in 6.19.9 with commit 85acaba2f42b557499bab3608307f17bf13beb69
Issue introduced in 3.11 with commit 40d133d7f542616cf9538508a372306e626a16e9 and fixed in 7.0 with commit ec35c1969650e7cb6c8a91020e568ed46e3551b0
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-2026-43421
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:
drivers/usb/gadget/function/f_ncm.c
drivers/usb/gadget/function/u_ether.c
drivers/usb/gadget/function/u_ether.h
drivers/usb/gadget/function/u_ncm.h
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/93f116c3393a22acab96ad1bef12b2572eb80ca4
https://git.kernel.org/stable/c/e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d
https://git.kernel.org/stable/c/85acaba2f42b557499bab3608307f17bf13beb69
https://git.kernel.org/stable/c/ec35c1969650e7cb6c8a91020e568ed46e3551b0
reply other threads:[~2026-05-08 14:26 UTC|newest]
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