From 74be98774dfbc5b8b795db726bd772e735d2edd4 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Wed, 16 Feb 2022 16:25:11 -0800 Subject: 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: 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. Fixes: 40ba17afdfab ("cxl/acpi: Introduce cxl_decoder objects") Reported-by: Ben Widawsky Tested-by: Ben Widawsky Reviewed-by: Ben Widawsky Link: https://lore.kernel.org/r/164505751190.4175768.13324905271463416712.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams --- drivers/cxl/core/port.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/cxl') diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c index 0fc1441be014..c1681248f322 100644 --- a/drivers/cxl/core/port.c +++ b/drivers/cxl/core/port.c @@ -251,6 +251,7 @@ static void cxl_decoder_release(struct device *dev) ida_free(&port->decoder_ida, cxld->id); kfree(cxld); + put_device(&port->dev); } static const struct device_type cxl_decoder_endpoint_type = { @@ -1202,7 +1203,10 @@ static struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port, if (rc < 0) goto err; + /* need parent to stick around to release the id */ + get_device(&port->dev); cxld->id = rc; + cxld->nr_targets = nr_targets; seqlock_init(&cxld->target_lock); dev = &cxld->dev; -- cgit v1.2.3