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

commit 92ee3c60ec 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>
[OP: backport to 5.4: adjusted context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: samuelliao <samuelliao@tencent.com>
This commit is contained in:
Takashi Iwai 2022-05-06 12:10:09 +03:00 committed by Jianping Liu
parent 033f9059dc
commit 1f9b52756c
3 changed files with 39 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/sound/pcm.h
View File

@ -395,6 +395,7 @@ struct snd_pcm_runtime {
wait_queue_head_t sleep; /* poll sleep */
wait_queue_head_t tsleep; /* transfer sleep */
struct fasync_struct *fasync;
struct mutex buffer_mutex; /* protect for buffer changes */
/* -- private section -- */
void *private_data;

2
sound/core/pcm.c
View File

@ -965,6 +965,7 @@ 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;
@ -996,6 +997,7 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
substream->runtime = NULL;
if (substream->timer)
spin_unlock_irq(&substream->timer->lock);
mutex_destroy(&runtime->buffer_mutex);
kfree(runtime);
put_pid(substream->pid);
substream->pid = NULL;

47
sound/core/pcm_native.c
View File

@ -630,33 +630,40 @@ static int snd_pcm_hw_params_choose(struct snd_pcm_substream *pcm,
return 0;
}
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
#define is_oss_stream(substream) ((substream)->oss.oss)
#else
#define is_oss_stream(substream) false
#endif
static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *params)
{
struct snd_pcm_runtime *runtime;
int err, usecs;
int err = 0, usecs;
unsigned int bits;
snd_pcm_uframes_t frames;
if (PCM_RUNTIME_CHECK(substream))
return -ENXIO;
runtime = substream->runtime;
mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream);
switch (runtime->status->state) {
case SNDRV_PCM_STATE_OPEN:
case SNDRV_PCM_STATE_SETUP:
case SNDRV_PCM_STATE_PREPARED:
if (!is_oss_stream(substream) &&
atomic_read(&substream->mmap_count))
err = -EBADFD;
break;
default:
snd_pcm_stream_unlock_irq(substream);
return -EBADFD;
err = -EBADFD;
break;
}
snd_pcm_stream_unlock_irq(substream);
#if IS_ENABLED(CONFIG_SND_PCM_OSS)
if (!substream->oss.oss)
#endif
if (atomic_read(&substream->mmap_count))
return -EBADFD;
if (err)
goto unlock;
params->rmask = ~0U;
err = snd_pcm_hw_refine(substream, params);
@ -733,14 +740,19 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
if ((usecs = period_to_usecs(runtime)) >= 0)
pm_qos_add_request(&substream->latency_pm_qos_req,
PM_QOS_CPU_DMA_LATENCY, usecs);
return 0;
err = 0;
_error:
if (err) {
/* hardware might be unusable from this time,
so we force application to retry to set
the correct hardware parameter settings */
* so we force application to retry to set
* the correct hardware parameter settings
*/
snd_pcm_set_state(substream, SNDRV_PCM_STATE_OPEN);
if (substream->ops->hw_free != NULL)
substream->ops->hw_free(substream);
}
unlock:
mutex_unlock(&runtime->buffer_mutex);
return err;
}
@ -773,22 +785,27 @@ static int snd_pcm_hw_free(struct snd_pcm_substream *substream)
if (PCM_RUNTIME_CHECK(substream))
return -ENXIO;
runtime = substream->runtime;
mutex_lock(&runtime->buffer_mutex);
snd_pcm_stream_lock_irq(substream);
switch (runtime->status->state) {
case SNDRV_PCM_STATE_SETUP:
case SNDRV_PCM_STATE_PREPARED:
if (atomic_read(&substream->mmap_count))
result = -EBADFD;
break;
default:
snd_pcm_stream_unlock_irq(substream);
return -EBADFD;
result = -EBADFD;
break;
}
snd_pcm_stream_unlock_irq(substream);
if (atomic_read(&substream->mmap_count))
return -EBADFD;
if (result)
goto unlock;
if (substream->ops->hw_free)
result = substream->ops->hw_free(substream);
snd_pcm_set_state(substream, SNDRV_PCM_STATE_OPEN);
pm_qos_remove_request(&substream->latency_pm_qos_req);
unlock:
mutex_unlock(&runtime->buffer_mutex);
return result;
}