From: Dan Williams Date: Thu, 17 Feb 2022 00:25:11 +0000 (-0800) Subject: cxl/port: Hold port reference until decoder release X-Git-Tag: v5.15.73~2520 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=518bb96367123062b48b0a9842f2864249b565f6;p=platform%2Fkernel%2Flinux-rpi.git cxl/port: Hold port reference until decoder release [ Upstream commit 74be98774dfbc5b8b795db726bd772e735d2edd4 ] 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 Signed-off-by: Sasha Levin --- diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c index 267d804..0987a64 100644 --- a/drivers/cxl/core/bus.c +++ b/drivers/cxl/core/bus.c @@ -182,6 +182,7 @@ 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_switch_type = { @@ -481,6 +482,9 @@ cxl_decoder_alloc(struct cxl_port *port, int nr_targets, resource_size_t base, if (rc < 0) goto err; + /* need parent to stick around to release the id */ + get_device(&port->dev); + *cxld = (struct cxl_decoder) { .id = rc, .range = {