CVE-2024-26897

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

wifi: ath9k: delay all of ath9k_wmi_event_tasklet() until init is complete

The ath9k_wmi_event_tasklet() used in ath9k_htc assumes that all the data structures have been fully initialised by the time it runs. However, because of the order in which things are initialised, this is not guaranteed to be the case, because the device is exposed to the USB subsystem before the ath9k driver initialisation is completed.

We already committed a partial fix for this in commit: 8b3046abc99e (ath9k_htc: fix NULL pointer dereference at ath9k_htc_tx_get_packet())

However, that commit only aborted the WMI_TXSTATUS_EVENTID command in the event tasklet, pairing it with an initialisation complete bit in the TX struct. It seems syzbot managed to trigger the race for one of the other commands as well, so lets just move the existing synchronisation bit to cover the whole tasklet (setting it at the end of ath9k_htc_probe_device() instead of inside ath9k_tx_init()).

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/1bc5461a21c56a36e2a7d81e152b90ce019a3905
• https://git.kernel.org/stable/c/24355fcb0d4cbcb6ddda262596558e8cfba70f11
• https://git.kernel.org/stable/c/4afa0246656d5680c8a4c3fb37ba6570c4ab819b
• https://git.kernel.org/stable/c/74d0639261dd795dce958d1b14815bdcbb48a715
• https://git.kernel.org/stable/c/a015fbf698c8957aa5fbeefc5c59dd2cf3107298
• https://git.kernel.org/stable/c/ac90e22e735bac44f74b5161fb096fbeb0ff8bc2
• https://git.kernel.org/stable/c/f8ff4b4df71e87f609be0cc37d92e918107f9b90
• https://git.kernel.org/stable/c/1bc5461a21c56a36e2a7d81e152b90ce019a3905
• https://git.kernel.org/stable/c/24355fcb0d4cbcb6ddda262596558e8cfba70f11
• https://git.kernel.org/stable/c/4afa0246656d5680c8a4c3fb37ba6570c4ab819b
• https://git.kernel.org/stable/c/74d0639261dd795dce958d1b14815bdcbb48a715
• https://git.kernel.org/stable/c/a015fbf698c8957aa5fbeefc5c59dd2cf3107298
• https://git.kernel.org/stable/c/ac90e22e735bac44f74b5161fb096fbeb0ff8bc2
• https://git.kernel.org/stable/c/f8ff4b4df71e87f609be0cc37d92e918107f9b90
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html