linux/sound/sh
Duoming Zhou 051e0840ff 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.

Fixes: 198de43d75 ("[ALSA] Add ALSA support for the SEGA Dreamcast PCM device")
Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Message-ID: <20240326094238.95442-1-duoming@zju.edu.cn>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2024-03-26 12:18:54 +01:00
..
aica.c ALSA: sh: aica: reorder cleanup operations to avoid UAF bugs 2024-03-26 12:18:54 +01:00
aica.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 273 2019-06-05 17:30:30 +02:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
sh_dac_audio.c ALSA: sh: Convert to generic PCM copy ops 2023-08-18 12:18:24 +02:00