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

[Takashi Iwai]

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
>