Vulnerability CVE-2024-39495
Published: 2024-07-12

Description:
In the Linux kernel, the following vulnerability has been resolved:

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

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.

 References:
https://git.kernel.org/stable/c/74cd0a421896b2e07eafe7da4275302bfecef201
https://git.kernel.org/stable/c/2b6bb0b4abfd79b8698ee161bb73c0936a2aaf83
https://git.kernel.org/stable/c/fb071f5c75d4b1c177824de74ee75f9dd34123b9
https://git.kernel.org/stable/c/9a733d69a4a59c2d08620e6589d823c24be773dc
https://git.kernel.org/stable/c/0b8fba38bdfb848fac52e71270b2aa3538c996ea
https://git.kernel.org/stable/c/03ea2b129344152157418929f06726989efc0445
https://git.kernel.org/stable/c/5c9c5d7f26acc2c669c1dcf57d1bb43ee99220ce
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