Linux Kernel up to 6.9-rc1 ALSA del_timer null pointer dereference

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 6.9-rc1. The impacted element is the function del_timer of the component ALSA. The manipulation results in null pointer dereference. This vulnerability is known as CVE-2024-26654. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.9-rc1. Affected is the function del_timer of the component ALSA. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ALSA: sh: aica: reorder cleanup operations to avoid UAF bugs The dreamcastcard->timer could schedule the spu_dma_work and the spu_dma_work could also arm the dreamcastcard->timer. When the snd_pcm_substream is closing, the aica_channel will be deallocated. But it could still be dereferenced in the worker thread. The reason is that del_timer() will return directly regardless of whether the timer handler is running or not and the worker could be rescheduled in the timer handler. As a result, the UAF bug will happen. The racy situation is shown below: (Thread 1) | (Thread 2) snd_aicapcm_pcm_close() | ... | run_spu_dma() //worker | mod_timer() flush_work() | del_timer() | aica_period_elapsed() //timer kfree(dreamcastcard->channel) | schedule_work() | run_spu_dma() //worker ... | dreamcastcard->channel-> //USE In order to mitigate this bug and other possible corner cases, call mod_timer() conditionally in run_spu_dma(), then implement PCM sync_stop op to cancel both the timer and worker. The sync_stop op will be called from PCM core appropriately when needed.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2024-26654 since 02/19/2024. Technical details are known, but there is no available exploit.

Upgrading to version 6.9-rc2 eliminates this vulnerability. Applying the patch 051e0840ffa8 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.9-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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