In the Linux kernel, the following vulnerability has been resolved:
i2c: core: fix debugfs UAF on adapter removal
i2c_del_adapter() frees the adapter’s debugfs directory before it
unregisters the adapter device, but the new_device sysfs attribute
stays writable until device_del(). A write racing with removal still
reaches i2c_device_probe(), which passes the freed adap->debugfs to
debugfs_create_dir() as the new client’s parent:
BUG: KASAN: slab-use-after-free in lookup_noperm_common+0x407/0x430
Read of size 4 at addr ffff88803ef87810 by task syz.0.61/6090
lookup_noperm_common+0x407/0x430
simple_start_creating+0x9c/0x110
debugfs_start_creating+0xdb/0x1a0
debugfs_create_dir+0x24/0x350
i2c_device_probe+0x814/0xbf0
It’s technically possible to create a client after i2c_deregister_clients
has run. That client will never be unregistered and make
wait_for_completion hang.
Close the window by removing the new_device attribute at the start of
i2c_del_adapter(). device_remove_file() will drain any clients left.
