CVE-2026-64455

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

USB: chaoskey: Fix slab-use-after-free in chaoskey_release()

The chaoskey driver has a use-after-free bug in its release routine. If the user closes the device file after the USB device has been unplugged, a debugging log statement will try to access the usb_interface structure after it has been deallocated:

BUG: KASAN: slab-use-after-free in dev_driver_string (drivers/base/core.c:2406)
Read of size 8 at addr ffff888168e8a0b8 by task chaoskey_raw_re/10106

Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
 print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
 kasan_report (mm/kasan/report.c:595)
 dev_driver_string (drivers/base/core.c:2406)
 __dynamic_dev_dbg (lib/dynamic_debug.c:906)
 chaoskey_release (drivers/usb/misc/chaoskey.c:323)
 __fput (fs/file_table.c:510)
 fput_close_sync (fs/file_table.c:615)
 __x64_sys_close (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492)
 do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
 entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

The driver's last reference to the interface structure is dropped in the chaoskey_free() routine, so the code must not use the interface -- even in a debugging statement -- after that routine returns. (Exception: If we know that another reference is held by someone else, such as the device core while the disconnect routine runs, there's no problem. Thanks to Johan Hovold for pointing this out.)

Since the bad access is part of an unimportant debugging statement, we can fix the problem simply by removing the whole statement.