CVE-2026-64453: usb: misc: usbio: fix disconnect UAF in client teardown

From: Greg Kroah-Hartman <[email protected]>

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

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

usb: misc: usbio: fix disconnect UAF in client teardown

usbio_disconnect() walks usbio->cli_list in reverse and uninitializes each
auxiliary device. auxiliary_device_uninit() drops the device reference, and
for an unbound child that can run usbio_auxdev_release() and free the
containing struct usbio_client.

list_for_each_entry_reverse() advances after the loop body by reading
client->link.prev. If the current client is freed by
auxiliary_device_uninit(), the iterator dereferences freed memory.

Use list_for_each_entry_safe_reverse() so the previous client is
cached before the body can drop the final reference. This preserves
reverse teardown order while keeping the next iterator cursor independent
of the current client's lifetime.

Validation reproduced this kernel report:
BUG: KASAN: slab-use-after-free in usbio_disconnect+0x12e/0x150

Call Trace:
 <TASK>
 dump_stack_lvl+0x66/0xa0
 print_report+0xce/0x630
 ? usbio_disconnect+0x12e/0x150
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __virt_addr_valid+0x188/0x320
 ? usbio_disconnect+0x12e/0x150
 kasan_report+0xe0/0x110
 ? usbio_disconnect+0x12e/0x150
 usbio_disconnect+0x12e/0x150
 usb_unbind_interface+0xf3/0x400
 really_probe+0x316/0x660
 __driver_probe_device+0x106/0x240
 driver_probe_device+0x4a/0x110
 __device_attach_driver+0xf1/0x1a0
 ? __pfx___device_attach_driver+0x10/0x10
 bus_for_each_drv+0xf9/0x160
 ? __pfx_bus_for_each_drv+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? trace_hardirqs_on+0x18/0x130
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? _raw_spin_unlock_irqrestore+0x44/0x60
 __device_attach+0x133/0x2a0
 ? __pfx___device_attach+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? do_raw_spin_unlock+0x9a/0x100
 ? srso_alias_return_thunk+0x5/0xfbef5
 device_initial_probe+0x55/0x70
 bus_probe_device+0x4a/0xd0
 device_add+0x9b9/0xc10
 ? __pfx_device_add+0x10/0x10
 ? _raw_spin_unlock_irqrestore+0x44/0x60
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lockdep_hardirqs_on_prepare+0xea/0x1a0
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? usb_enable_lpm+0x3c/0x260
 usb_set_configuration+0xb64/0xf20
 usb_generic_driver_probe+0x5f/0x90
 usb_probe_device+0x71/0x1b0
 really_probe+0x46b/0x660
 __driver_probe_device+0x106/0x240
 driver_probe_device+0x4a/0x110
 __device_attach_driver+0xf1/0x1a0
 ? __pfx___device_attach_driver+0x10/0x10
 bus_for_each_drv+0xf9/0x160
 ? __pfx_bus_for_each_drv+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? trace_hardirqs_on+0x18/0x130
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? _raw_spin_unlock_irqrestore+0x44/0x60
 __device_attach+0x133/0x2a0
 ? __pfx___device_attach+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? do_raw_spin_unlock+0x9a/0x100
 ? srso_alias_return_thunk+0x5/0xfbef5
 device_initial_probe+0x55/0x70
 bus_probe_device+0x4a/0xd0
 device_add+0x9b9/0xc10
 ? __pfx_device_add+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? add_device_randomness+0xb7/0xf0
 usb_new_device+0x492/0x870
 hub_event+0x1b10/0x29c0
 ? __pfx_hub_event+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lock_acquire+0x187/0x300
 ? process_one_work+0x475/0xb90
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lock_release+0xc8/0x290
 ? srso_alias_return_thunk+0x5/0xfbef5
 process_one_work+0x4d7/0xb90
 ? __pfx_process_one_work+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __list_add_valid_or_report+0x37/0xf0
 ? __pfx_hub_event+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 worker_thread+0x2d8/0x570
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x1ad/0x1f0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x3c9/0x540
 ? __pfx_ret_from_fork+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __switch_to+0x2e9/0x730
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1a/0x30
 </TASK>

The Linux kernel CVE team has assigned CVE-2026-64453 to this issue.


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

	Issue introduced in 6.18 with commit 121a0f839dbb397af5fabb701cea3e9983223e50 and fixed in 6.18.39 with commit c40090f8d19b415e2925b22be964b5d1f695666f
	Issue introduced in 6.18 with commit 121a0f839dbb397af5fabb701cea3e9983223e50 and fixed in 7.1.4 with commit 1947b6411460d68b54b13c536961933166937d05
	Issue introduced in 6.18 with commit 121a0f839dbb397af5fabb701cea3e9983223e50 and fixed in 7.2-rc3 with commit 0bfeec21984fedd32987f4e4c0cde34b445af404

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-2026-64453
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/misc/usbio.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/c40090f8d19b415e2925b22be964b5d1f695666f
	https://git.kernel.org/stable/c/1947b6411460d68b54b13c536961933166937d05
	https://git.kernel.org/stable/c/0bfeec21984fedd32987f4e4c0cde34b445af404