From: Dan Williams dan.j.williams@intel.com
[ 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: <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.
Fixes: 40ba17afdfab ("cxl/acpi: Introduce cxl_decoder objects") Reported-by: Ben Widawsky ben.widawsky@intel.com Tested-by: Ben Widawsky ben.widawsky@intel.com Reviewed-by: Ben Widawsky ben.widawsky@intel.com Link: https://lore.kernel.org/r/164505751190.4175768.13324905271463416712.stgit@dw... Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cxl/core/bus.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/cxl/core/bus.c b/drivers/cxl/core/bus.c index 46ce58376580..55e120350a29 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 = { @@ -500,7 +501,10 @@ struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port, int nr_targets) 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; dev = &cxld->dev; device_initialize(dev);