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

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Date:   Tue, 12 Nov 2019 19:16:50 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     paulhsia <paulhsia@...omium.org>
Cc:     linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org
Subject: Re: [PATCH 0/2] ALSA: pcm: Fix race condition in runtime access

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
>