CVE-2026-89735: usb: gadget: midi2: remove default configfs groups on teardown

CVE-2026-89735: usb: gadget: midi2: remove default configfs groups on teardown

[Greg Kroah-Hartman]

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

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

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

usb: gadget: midi2: remove default configfs groups on teardown

f_midi2_alloc_inst() creates default configfs child groups for the
default endpoint and default block using configfs_add_default_group(),
setting their internal refcount to 1.

However, during function teardown in f_midi2_free_inst() or EP cleanup
in f_midi2_ep_opts_release(), configfs_remove_default_groups() is
never called, therefore never dropping the refcount and leaking struct
f_midi2_ep_opts and f_midi2_block_opts.

Add the missing configfs_remove_default_groups() in the afformentioned
functions to free the structs properly.

The Linux kernel CVE team has assigned CVE-2026-89735 to this issue.


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

	Issue introduced in 6.6 with commit 8b645922b22303cec4628dbbbf6c8553d1cdec87 and fixed in 6.12.109 with commit 4beda67ee72e0c8df5b49951dd8b96f6adb25e02
	Issue introduced in 6.6 with commit 8b645922b22303cec4628dbbbf6c8553d1cdec87 and fixed in 6.18.50 with commit a15c2acd3083461f91725760e59dff88b33c28f6
	Issue introduced in 6.6 with commit 8b645922b22303cec4628dbbbf6c8553d1cdec87 and fixed in 7.2.4 with commit 9ea5dfb2bfef4f8a7e704d1921d8a790cb7fb700
	Issue introduced in 6.6 with commit 8b645922b22303cec4628dbbbf6c8553d1cdec87 and fixed in 7.3-rc1 with commit 0f6bffb5008f0cba9cad5ded2caccc64466a6e54

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-2026-89735
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_midi2.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/4beda67ee72e0c8df5b49951dd8b96f6adb25e02
	https://git.kernel.org/stable/c/a15c2acd3083461f91725760e59dff88b33c28f6
	https://git.kernel.org/stable/c/9ea5dfb2bfef4f8a7e704d1921d8a790cb7fb700
	https://git.kernel.org/stable/c/0f6bffb5008f0cba9cad5ded2caccc64466a6e54