CVE-2024-38600

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

ALSA: Fix deadlocks with kctl removals at disconnection

In snd_card_disconnect(), we set card->shutdown flag at the beginning, call callbacks and do sync for card->power_ref_sleep waiters at the end. The callback may delete a kctl element, and this can lead to a deadlock when the device was in the suspended state. Namely:

• A process waits for the power up at snd_power_ref_and_wait() in snd_ctl_info() or read/write() inside card->controls_rwsem.

• The system gets disconnected meanwhile, and the driver tries to delete a kctl via snd_ctl_remove*(); it tries to take card->controls_rwsem again, but this is already locked by the above. Since the sleeper isnt woken up, this deadlocks.

An easy fix is to wake up sleepers before processing the driver disconnect callbacks but right after setting the card->shutdown flag. Then all sleepers will abort immediately, and the code flows again.

So, basically this patch moves the wait_event() call at the right timing. While were at it, just to be sure, call wait_event_all() instead of wait_event(), although we dont use exclusive events on this queue for now.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/2f103287ef7960854808930499d1181bd0145d68
• https://git.kernel.org/stable/c/6b55e879e7bd023a03888fc6c8339edf82f576f4
• https://git.kernel.org/stable/c/87988a534d8e12f2e6fc01fe63e6c1925dc5307c
• https://git.kernel.org/stable/c/88ce3fe255d58a93624b467af036dc3519f309c7
• https://git.kernel.org/stable/c/c2fb439f4f1425a961d20bec818fed2c2d9ef70a
• https://git.kernel.org/stable/c/ff80185e7b7b547a0911fcfc8aefc61c3e8304d7