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

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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>
This commit is contained in:
Takashi Iwai 2022-03-22 18:07:17 +01:00
parent 646b907e15
commit 92ee3c60ec
3 changed files with 42 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
include/sound/pcm.h
View file

@ -401,6 +401,7 @@ struct snd_pcm_runtime {
wait_queue_head_t tsleep; /* transfer sleep */
struct fasync_struct *fasync;
bool stop_operating; /* sync_stop will be called */
struct mutex buffer_mutex; /* protect for buffer changes */
/* -- private section -- */
void *private_data;

2
sound/core/pcm.c
View file

@ -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;

61
sound/core/pcm_native.c
View file

@ -685,33 +685,40 @@ 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;
snd_pcm_sync_stop(substream, true);
@ -799,16 +806,21 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
if (usecs >= 0)
cpu_latency_qos_add_request(&substream->latency_pm_qos_req,
usecs);
return 0;
err = 0;
_error:
/* hardware might be unusable from this time,
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);
if (substream->managed_buffer_alloc)
snd_pcm_lib_free_pages(substream);
if (err) {
/* hardware might be unusable from this time,
* 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);
if (substream->managed_buffer_alloc)
snd_pcm_lib_free_pages(substream);
}
unlock:
mutex_unlock(&runtime->buffer_mutex);
return err;
}
@ -848,26 +860,31 @@ static int do_hw_free(struct snd_pcm_substream *substream)
static int snd_pcm_hw_free(struct snd_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime;
int result;
int result = 0;
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;
result = do_hw_free(substream);
snd_pcm_set_state(substream, SNDRV_PCM_STATE_OPEN);
cpu_latency_qos_remove_request(&substream->latency_pm_qos_req);
unlock:
mutex_unlock(&runtime->buffer_mutex);
return result;
}