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ALSA: pcm: Fix races among concurrent hw_params and hw_free calls

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commit 92ee3c60ec9fe64404dc035e7c41277d74aa26cb upstream.

Currently we have neither proper check nor protection against the
concurrent calls of PCM hw_params and hw_free ioctls, which may result
in a UAF.  Since the existing PCM stream lock can't be used for
protecting the whole ioctl operations, we need a new mutex to protect
those racy calls.

This patch introduced a new mutex, runtime->buffer_mutex, and applies
it to both hw_params and hw_free ioctl code paths.  Along with it, the
both functions are slightly modified (the mmap_count check is moved
into the state-check block) for code simplicity.

Reported-by: Hu Jiahui <kirin.say@gmail.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai
2022-03-22 18:07:17 +01:00
committed by Greg Kroah-Hartman
parent 014c81dfb3
commit 0f6947f5f5
3 changed files with 42 additions and 22 deletions
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2
sound/core/pcm.c
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@@ -969,6 +969,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
init_waitqueue_head(&runtime->tsleep);
runtime->status->state = SNDRV_PCM_STATE_OPEN;
mutex_init(&runtime->buffer_mutex);
substream->runtime = runtime;
substream->private_data = pcm->private_data;
@@ -1002,6 +1003,7 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
} else {
substream->runtime = NULL;
}
mutex_destroy(&runtime->buffer_mutex);
kfree(runtime);
put_pid(substream->pid);
substream->pid = NULL;