CVE-2022-49968

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

ieee802154/adf7242: defer destroy_workqueue call

There is a possible race condition (use-after-free) like below

(FREE) | (USE) adf7242_remove | adf7242_channel cancel_delayed_work_sync | destroy_workqueue (1) | adf7242_cmd_rx | mod_delayed_work (2) |

The root cause for this race is that the upper layer (ieee802154) is unaware of this detaching event and the function adf7242_channel can be called without any checks.

To fix this, we can add a flag write at the beginning of adf7242_remove and add flag check in adf7242_channel. Or we can just defer the destructive operation like other commit 3e0588c291d6 (hamradio: defer ax25 kfree after unregister_netdev) which let the ieee802154_unregister_hw() to handle the synchronization. This patch takes the second option.

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Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/15f3b89bd521d5770d36a61fc04a77c293138ba6
• https://git.kernel.org/stable/c/23a29932715ca43bceb2eae1bdb770995afe7271
• https://git.kernel.org/stable/c/9f8558c5c642c62c450c98c99b7d18a709fff485
• https://git.kernel.org/stable/c/afe7116f6d3b888778ed6d95e3cf724767b9aedf
• https://git.kernel.org/stable/c/bed12d7531df1417fc92c691999ff95e03835008
• https://git.kernel.org/stable/c/dede80aaf01f4b6e8657d23726cb4a3da226ec4c