Re: [PATCH 0/2] ALSA: pcm: Fix race condition in runtime access

Takashi Iwai
2019-11-12T18:16:54Z

On Tue, 12 Nov 2019 18:17:13 +0100,
paulhsia wrote:
>
> Since
> - snd_pcm_detach_substream sets runtime to null without stream lock and
> - snd_pcm_period_elapsed checks the nullity of the runtime outside of
> stream lock.
>
> This will trigger null memory access in snd_pcm_running() call in
> snd_pcm_period_elapsed.

Well, if a stream is detached, it means that the stream must have been
already closed; i.e. it's already a clear bug in the driver that
snd_pcm_period_elapsed() is called against such a stream.

Or am I missing other possible case?

thanks,

Takashi

>
> paulhsia (2):
> ALSA: pcm: Fix stream lock usage in snd_pcm_period_elapsed()
> ALSA: pcm: Use stream lock in snd_pcm_detach_substream()
>
> sound/core/pcm.c | 8 +++++++-
> sound/core/pcm_lib.c | 8 ++++++--
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> --
> 2.24.0.rc1.363.gb1bccd3e3d-goog
>