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

commit 5c9c5d7f26acc2c669c1dcf57d1bb43ee99220ce upstream.

In gb_interface_create, &intf->mode_switch_completion is bou

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

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>

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