greybus: Fix use-after-free bug in gb_interface_release due to race condition.

BugLink: https://bugs.launchpad.net/bugs/2074091
commit 5c9c5d7f26acc2c669c1dcf57d1bb43ee99220ce upstream.

In gb_interface_create, &intf->mode_switch_completion is bound with
gb_interface_mode_switch_work. Then it will be started by
gb_interface_request_mode_switch. Here is the relevant code.
if (!queue_work(system_long_wq, &intf->mode_switch_work)) {
	...
}

If we call gb_interface_release to make cleanup, there may be an
unfinished work. This function will call kfree to free the object
"intf". However, if gb_interface_mode_switch_work is scheduled to
run after kfree, it may cause use-after-free error as
gb_interface_mode_switch_work will use the object "intf".
The possible execution flow that may lead to the issue is as follows:

CPU0                            CPU1

                            |   gb_interface_create
                            |   gb_interface_request_mode_switch
gb_interface_release        |
kfree(intf) (free)          |
                            |   gb_interface_mode_switch_work
                            |   mutex_lock(&intf->mutex) (use)

Fix it by canceling the work before kfree.

Signed-off-by: Sicong Huang <congei42@163.com>
Link: https://lore.kernel.org/r/20240416080313.92306-1-congei42@163.com
Cc: Ronnie Sahlberg <rsahlberg@ciq.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Portia Stephens <portia.stephens@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

diff --git a/drivers/greybus/interface.c b/drivers/greybus/interface.c
index 9ec949a438ef6752607a5ac2708294f12879ce64..52ef6be9d4499654483f0bfb112a3c411f65033a 100644 (file)
--- a/drivers/greybus/interface.c
+++ b/drivers/greybus/interface.c
@@ -694,6 +694,7 @@ static void gb_interface_release(struct device *dev)
 
        trace_gb_interface_release(intf);
 
+       cancel_work_sync(&intf->mode_switch_work);
        kfree(intf);
 }