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.
git.kernel.org/stable/c/051e0840ffa8ab25554d6b14b62c9ab9e4901457
git.kernel.org/stable/c/3c907bf56905de7d27b329afaf59c2fb35d17b04
git.kernel.org/stable/c/4206ad65a0ee76920041a755bd3c17c6ba59bba2
git.kernel.org/stable/c/61d4787692c1fccdc268ffa7a891f9c149f50901
git.kernel.org/stable/c/8c990221681688da34295d6d76cc2f5b963e83f5
git.kernel.org/stable/c/9d66ae0e7bb78b54e1e0525456c6b54e1d132046
git.kernel.org/stable/c/aa39e6878f61f50892ee2dd9d2176f72020be845
git.kernel.org/stable/c/e955e8a7f38a856fc6534ba4e6bffd4d5cc80ac3
git.kernel.org/stable/c/eeb2a2ca0b8de7e1c66afaf719529154e7dc60b2
lists.debian.org/debian-lts-announce/2024/06/msg00017.html