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audio: pipewire: Don't use uninitialized variables in callbacks 

Some of the SDL_AudioDevice struct members aren't initialized until after returning from the OpenDevice function.  Since Pipewire uses it's own processing threads, the callbacks can be entered before all members of SDL_AudioDevice are initialized, such as work_buffer, callbackspec and the processing stream, which creates a race condition.  Don't use these members when in the paused state to avoid potentially using uninitialized values and memory.
main
Frank Praznik 2021-03-28 17:17:00 -04:00 committed by Sam Lantinga
parent 9de7eaf9ac
commit 5bb2bbd40c
2 changed files with 29 additions and 29 deletions
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57
src/audio/pipewire/SDL_pipewire.c
View File

@ -893,14 +893,14 @@ output_callback(void *data)
* and run the callback with the work buffer to keep the callback
* firing regularly in case the audio is being used as a timer.
*/
if (SDL_AtomicGet(&this->enabled)) {
dst = spa_buf->datas[0].data;
} else {
dst = this->work_buffer;
SDL_memset(spa_buf->datas[0].data, this->spec.silence, this->spec.size);
}
if (!SDL_AtomicGet(&this->paused)) {
if (SDL_AtomicGet(&this->enabled)) {
dst = spa_buf->datas[0].data;
} else {
dst = this->work_buffer;
SDL_memset(spa_buf->datas[0].data, this->spec.silence, this->spec.size);
}
if (!this->stream) {
SDL_LockMutex(this->mixer_lock);
this->callbackspec.callback(this->callbackspec.userdata, dst, this->callbackspec.size);
@ -920,8 +920,8 @@ output_callback(void *data)
got = SDL_AudioStreamGet(this->stream, dst, this->spec.size);
SDL_assert(got == this->spec.size);
}
} else if (dst != this->work_buffer) {
SDL_memset(dst, this->spec.silence, this->spec.size);
} else {
SDL_memset(spa_buf->datas[0].data, this->spec.silence, this->spec.size);
}
spa_buf->datas[0].chunk->offset = 0;
@ -939,7 +939,6 @@ input_callback(void *data)
Uint8 * src;
_THIS = (SDL_AudioDevice *)data;
struct pw_stream *stream = this->hidden->stream;
Uint32 offset, size;
/* Shutting down, don't do anything */
if (SDL_AtomicGet(&this->shutdown)) {
@ -957,21 +956,21 @@ input_callback(void *data)
return;
}
/* Calculate the offset and data size */
offset = SPA_MIN(spa_buf->datas[0].chunk->offset, spa_buf->datas[0].maxsize);
size = SPA_MIN(spa_buf->datas[0].chunk->size, spa_buf->datas[0].maxsize - offset);
src += offset;
/* Fill the buffer with silence if the stream is disabled. */
if (!SDL_AtomicGet(&this->enabled)) {
SDL_memset(src, this->callbackspec.silence, size);
}
/* Pipewire can vary the latency, so buffer all incoming data */
SDL_WriteToDataQueue(this->hidden->buffer, src, size);
if (!SDL_AtomicGet(&this->paused)) {
/* Calculate the offset and data size */
const Uint32 offset = SPA_MIN(spa_buf->datas[0].chunk->offset, spa_buf->datas[0].maxsize);
const Uint32 size = SPA_MIN(spa_buf->datas[0].chunk->size, spa_buf->datas[0].maxsize - offset);
src += offset;
/* Fill the buffer with silence if the stream is disabled. */
if (!SDL_AtomicGet(&this->enabled)) {
SDL_memset(src, this->callbackspec.silence, size);
}
/* Pipewire can vary the latency, so buffer all incoming data */
SDL_WriteToDataQueue(this->hidden->buffer, src, size);
while (SDL_CountDataQueue(this->hidden->buffer) >= this->callbackspec.size) {
SDL_ReadFromDataQueue(this->hidden->buffer, this->work_buffer, this->callbackspec.size);
@ -979,9 +978,9 @@ input_callback(void *data)
this->callbackspec.callback(this->callbackspec.userdata, this->work_buffer, this->callbackspec.size);
SDL_UnlockMutex(this->mixer_lock);
}
} else { /* Keep data moving through the buffer while paused */
while (SDL_CountDataQueue(this->hidden->buffer) >= this->callbackspec.size) {
SDL_ReadFromDataQueue(this->hidden->buffer, this->work_buffer, this->callbackspec.size);
} else { /* Flush the buffer when paused */
if (SDL_CountDataQueue(this->hidden->buffer) != 0) {
SDL_ClearDataQueue(this->hidden->buffer, this->hidden->buffer_period_size * 2);
}
}
@ -1060,10 +1059,10 @@ PIPEWIRE_OpenDevice(_THIS, void *handle, const char *devname, int iscapture)
/* The latency of source nodes can change, so buffering is required. */
if (iscapture) {
const size_t period_size = adjusted_samples * priv->stride;
priv->buffer_period_size = SPA_MAX(this->spec.samples, adjusted_samples) * priv->stride;
/* A packet size of 4 periods should be more than is ever needed (no more than 2 should be queued in practice). */
priv->buffer = SDL_NewDataQueue(period_size * 4, period_size * 2);
priv->buffer = SDL_NewDataQueue(priv->buffer_period_size * 4, priv->buffer_period_size * 2);
if (priv->buffer == NULL) {
return SDL_SetError("Pipewire: Failed to allocate source buffer");
}

1
src/audio/pipewire/SDL_pipewire.h
View File

@ -37,6 +37,7 @@ struct SDL_PrivateAudioData
struct pw_context *context;
struct SDL_DataQueue *buffer;
size_t buffer_period_size;
Sint32 stride; /* Bytes-per-frame */
};