cxl/port: Hold port reference until decoder release

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: cxl/port: Hold port reference until decoder release KASAN + DEBUG_KOBJECT_RELEASE reports a potential use-after-free in cxl_decoder_release() where it goes to reference its parent, a cxl_port, to free its id back to port->decoder_ida. BUG: KASAN: use-after-free in to_cxl_port+0x18/0x90 [cxl_core] Read of size 8 at addr ffff888119270908 by task kworker/35:2/379 CPU: 35 PID: 379 Comm: kworker/35:2 Tainted: G OE 5.17.0-rc2+ #198 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: events kobject_delayed_cleanup Call Trace: <TASK> dump_stack_lvl+0x59/0x73 print_address_description.constprop.0+0x1f/0x150 ? to_cxl_port+0x18/0x90 [cxl_core] kasan_report.cold+0x83/0xdf ? to_cxl_port+0x18/0x90 [cxl_core] to_cxl_port+0x18/0x90 [cxl_core] cxl_decoder_release+0x2a/0x60 [cxl_core] device_release+0x5f/0x100 kobject_cleanup+0x80/0x1c0 The device core only guarantees parent lifetime until all children are unregistered. If a child needs a parent to complete its ->release() callback that child needs to hold a reference to extend the lifetime of the parent.

References

• https://git.kernel.org/stable/c/518bb96367123062b48b0a9842f2864249b565f6
• https://git.kernel.org/stable/c/b0022ca445d5fc4d0c89d15dcd0f855977b22c1d
• https://git.kernel.org/stable/c/49f2dab77a5e1354f5da6ccdc9346a8212697be2
• https://git.kernel.org/stable/c/74be98774dfbc5b8b795db726bd772e735d2edd4