From: Takashi Iwai tiwai@suse.de
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 [OP: backport to 4.14: adjusted context] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/sound/pcm.h | 1 sound/core/pcm.c | 2 + sound/core/pcm_native.c | 55 +++++++++++++++++++++++++++++++----------------- 3 files changed, 39 insertions(+), 19 deletions(-)
--- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -396,6 +396,7 @@ 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; --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -1032,6 +1032,7 @@ int snd_pcm_attach_substream(struct snd_ 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; @@ -1063,6 +1064,7 @@ void snd_pcm_detach_substream(struct snd 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; --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -634,33 +634,40 @@ static int snd_pcm_hw_params_choose(stru 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); @@ -737,14 +744,19 @@ static int snd_pcm_hw_params(struct snd_ 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: - /* 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 (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); + } + unlock: + mutex_unlock(&runtime->buffer_mutex); return err; }
@@ -777,22 +789,27 @@ static int snd_pcm_hw_free(struct snd_pc 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; }