CVE-2024-26654

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.