CVE-2026-80824: usb: usbfs: fix use-after-free of usb_device in usbdev_release()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

usb: usbfs: fix use-after-free of usb_device in usbdev_release()

usbdev_release() drops its reference to the struct usb_device before
draining the list of completed async URBs, but that drain path reads back
through the same object: free_async() calls dec_usb_memory_use_count()
for any URB whose buffer came from the usbfs mmap() region, and its first
statement is bus_to_hcd(ps->dev->bus).

After a disconnect the usbfs reference can be the last one, in which case
usb_put_dev() frees the device and the subsequent loop reads offset 80 of
freed memory and uses the result as a struct usb_hcd *, which
hcd_buffer_free_pages() then dereferences.

This is reachable by an unprivileged process that has read/write access to
a /dev/bus/usb node: mmap() the fd, submit one URB with a buffer inside the
mapping, wait for the device to be unplugged, then munmap() and close().
It reproduces on every attempt rather than being a race, because a live
MAP_SHARED vma holds a reference on the struct file, so usbdev_release()
cannot run until the last vma is gone and the freeing branch of
dec_usb_memory_use_count() is always taken.

  BUG: KASAN: slab-use-after-free in dec_usb_memory_use_count+0x3ae/0x410
  Read of size 8 at addr ffff8880122ee050 by task poc/769
  CPU: 1 UID: 1000 PID: 769 Comm: poc Tainted: G    B    6.12.94 #3

  Call Trace:
   dec_usb_memory_use_count+0x3ae/0x410
   free_async+0x2aa/0x4f0
   usbdev_release+0x375/0x460
   __fput+0x3ea/0xb50
   __x64_sys_close+0x86/0x100

  Allocated by task 11:
   usb_alloc_dev+0x55/0xd90
   hub_event+0x2524/0x43d0

  Freed by task 769:
   kfree+0x121/0x360
   device_release+0xd2/0x280
   usb_put_dev+0x23/0x30
   usbdev_release+0x2d8/0x460

Release the device reference after the drain loop instead. Nothing between
the two points requires it to have been dropped.

The Linux kernel CVE team has assigned CVE-2026-80824 to this issue.


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

	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 5.10.269 with commit 0a960b88c5979f853019d4dc4957dfbeeb193440
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 5.15.220 with commit 96f5520fc9a5e4bbf77ac93c9d5ce502f597e6cf
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 6.1.187 with commit bd4bffc621a8cb2f4d9ed9b6447415de524a3bef
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 6.6.156 with commit 65879e0a452ca2a234b9475e0c11aff7a4343738
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 6.12.108 with commit b3cde26a66b04f1d90ed0b675899c88b4e49d424
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 6.18.49 with commit 5f08c45bdcfd28d1171de38c5ef29fc89a76eedc
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 7.1.13 with commit 7f0278e474c4d1c4457974ff1137cc385c944ab3
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 7.2.3 with commit 47a7f98fbb5006d46d15a3a210ffdc61448a4f19
	Issue introduced in 4.6 with commit f7d34b445abc00e979b7cf36b9580ac3d1a47cd8 and fixed in 7.3-rc1 with commit 0dd68b5d01d022fc9c5e71c82a82b0a94d3d0671

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-2026-80824
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/core/devio.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/0a960b88c5979f853019d4dc4957dfbeeb193440
	https://git.kernel.org/stable/c/96f5520fc9a5e4bbf77ac93c9d5ce502f597e6cf
	https://git.kernel.org/stable/c/bd4bffc621a8cb2f4d9ed9b6447415de524a3bef
	https://git.kernel.org/stable/c/65879e0a452ca2a234b9475e0c11aff7a4343738
	https://git.kernel.org/stable/c/b3cde26a66b04f1d90ed0b675899c88b4e49d424
	https://git.kernel.org/stable/c/5f08c45bdcfd28d1171de38c5ef29fc89a76eedc
	https://git.kernel.org/stable/c/7f0278e474c4d1c4457974ff1137cc385c944ab3
	https://git.kernel.org/stable/c/47a7f98fbb5006d46d15a3a210ffdc61448a4f19
	https://git.kernel.org/stable/c/0dd68b5d01d022fc9c5e71c82a82b0a94d3d0671