[RFC PATCH v2 4/5] ASoC: soc-pcm: protect for_each_dpcm_be() loops with dpcm_mutex
Pierre-Louis Bossart
pierre-louis.bossart at linux.intel.com
Tue Oct 5 00:54:40 CEST 2021
When more than one FE is connected to a BE, e.g. in a mixing use case,
the BE can be triggered multiple times when the FE are opened/started
concurrently. This race condition is problematic in the case of
SoundWire BE dailinks, and this is not desirable in a general
case. The code carefully checks when the BE can be stopped or
hw_free'ed, but the trigger code does not use any mutual exclusion.
This can be fixed by using the dpcm_mutex.
As discussed on the alsa-mailing list [1], there is an additional
issue that the BEs can be disconnected dynamically, leading to
potential accesses to freed memory.
This patch suggests a general protection of the for_each_dpcm_be()
loop with the dpcm_mutex, to solve both the problem of multiple
triggers and BE dynamic addition/removal.
[1] https://lore.kernel.org/alsa-devel/002f01d7b4f5$c030f4a0$4092dde0$@samsung.com/
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
sound/soc/soc-pcm.c | 48 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 39 insertions(+), 9 deletions(-)
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index af12593b033a..6089e0c1bf9f 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -320,6 +320,7 @@ int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
{
struct snd_soc_dpcm *dpcm;
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, dir, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
@@ -333,6 +334,8 @@ int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
snd_soc_dapm_stream_event(be, dir, event);
}
+ mutex_unlock(&fe->card->dpcm_mutex);
+
snd_soc_dapm_stream_event(fe, dir, event);
@@ -1142,10 +1145,14 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
struct snd_soc_dpcm *dpcm;
/* only add new dpcms */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
- if (dpcm->be == be && dpcm->fe == fe)
+ if (dpcm->be == be && dpcm->fe == fe) {
+ mutex_unlock(&fe->card->dpcm_mutex);
return 0;
+ }
}
+ mutex_unlock(&fe->card->dpcm_mutex);
dpcm = kzalloc(sizeof(struct snd_soc_dpcm), GFP_KERNEL);
if (!dpcm)
@@ -1202,6 +1209,7 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
{
struct snd_soc_dpcm *dpcm, *d;
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be_safe(fe, stream, dpcm, d) {
dev_dbg(fe->dev, "ASoC: BE %s disconnect check for %s\n",
stream ? "capture" : "playback",
@@ -1219,12 +1227,11 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
dpcm_remove_debugfs_state(dpcm);
- mutex_lock(&fe->card->dpcm_mutex);
list_del(&dpcm->list_be);
list_del(&dpcm->list_fe);
- mutex_unlock(&fe->card->dpcm_mutex);
kfree(dpcm);
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
/* get BE for DAI widget and stream */
@@ -1351,6 +1358,7 @@ static int dpcm_prune_paths(struct snd_soc_pcm_runtime *fe, int stream,
int prune = 0;
/* Destroy any old FE <--> BE connections */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
if (dpcm_be_is_active(dpcm, stream, *list_))
continue;
@@ -1362,6 +1370,7 @@ static int dpcm_prune_paths(struct snd_soc_pcm_runtime *fe, int stream,
dpcm_set_be_update_state(dpcm->be, stream, SND_SOC_DPCM_UPDATE_BE);
prune++;
}
+ mutex_unlock(&fe->card->dpcm_mutex);
dev_dbg(fe->dev, "ASoC: found %d old BE paths for pruning\n", prune);
return prune;
@@ -1451,13 +1460,16 @@ void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
struct snd_soc_dpcm *dpcm;
/* disable any enabled and non active backends */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
struct snd_pcm_substream *be_substream =
snd_soc_dpcm_get_substream(be, stream);
- if (dpcm == last)
+ if (dpcm == last) {
+ mutex_unlock(&fe->card->dpcm_mutex);
return;
+ }
/* is this op for this BE ? */
if (!snd_soc_dpcm_be_can_update(fe, be, stream))
@@ -1487,6 +1499,7 @@ void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
be_substream->runtime = NULL;
be->dpcm[stream].state = SND_SOC_DPCM_STATE_CLOSE;
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
@@ -1496,6 +1509,7 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
int err, count = 0;
/* only startup BE DAIs that are either sinks or sources to this FE DAI */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_pcm_substream *be_substream;
@@ -1546,11 +1560,13 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
be->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
count++;
}
+ mutex_unlock(&fe->card->dpcm_mutex);
return count;
unwind:
dpcm_be_dai_startup_rollback(fe, stream, dpcm);
+ mutex_unlock(&fe->card->dpcm_mutex);
dev_err(fe->dev, "ASoC: %s() failed at %s (%d)\n",
__func__, be->dai_link->name, err);
@@ -1605,6 +1621,7 @@ static void dpcm_runtime_setup_be_format(struct snd_pcm_substream *substream)
* if FE want to use it (= dpcm_merged_format)
*/
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
struct snd_soc_pcm_stream *codec_stream;
@@ -1623,6 +1640,7 @@ static void dpcm_runtime_setup_be_format(struct snd_pcm_substream *substream)
soc_pcm_hw_update_format(hw, codec_stream);
}
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
@@ -1640,7 +1658,7 @@ static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
* It returns merged BE codec channel;
* if FE want to use it (= dpcm_merged_chan)
*/
-
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
struct snd_soc_pcm_stream *cpu_stream;
@@ -1671,6 +1689,7 @@ static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
soc_pcm_hw_update_chan(hw, codec_stream);
}
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
@@ -1688,7 +1707,7 @@ static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
* It returns merged BE codec channel;
* if FE want to use it (= dpcm_merged_chan)
*/
-
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
struct snd_soc_pcm_stream *pcm;
@@ -1708,6 +1727,7 @@ static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
soc_pcm_hw_update_rate(hw, pcm);
}
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
@@ -1730,6 +1750,7 @@ static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
}
/* apply symmetry for BE */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
struct snd_pcm_substream *be_substream =
@@ -1755,6 +1776,7 @@ static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
}
}
error:
+ mutex_unlock(&fe->card->dpcm_mutex);
if (err < 0)
dev_err(fe->dev, "ASoC: %s failed (%d)\n", __func__, err);
@@ -1830,6 +1852,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
/* only hw_params backends that are either sinks or sources
* to this frontend DAI */
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_soc_pcm_runtime *be = dpcm->be;
@@ -1842,7 +1865,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
/* only free hw when no longer used - check all FEs */
if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
- continue;
+ continue;
/* do not free hw if this BE is used by other FE */
if (be->dpcm[stream].users > 1)
@@ -1863,6 +1886,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_FREE;
}
+ mutex_unlock(&fe->card->dpcm_mutex);
}
static int dpcm_fe_dai_hw_free(struct snd_pcm_substream *substream)
@@ -1896,6 +1920,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
struct snd_soc_dpcm *dpcm;
int ret;
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
be = dpcm->be;
be_substream = snd_soc_dpcm_get_substream(be, stream);
@@ -1935,6 +1960,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_PARAMS;
}
+ mutex_unlock(&fe->card->dpcm_mutex);
return 0;
unwind:
@@ -1961,6 +1987,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
soc_pcm_hw_free(be_substream);
}
+ mutex_unlock(&fe->card->dpcm_mutex);
return ret;
}
@@ -2008,6 +2035,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
struct snd_soc_dpcm *dpcm;
int ret = 0;
+ mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_be(fe, stream, dpcm) {
struct snd_pcm_substream *be_substream;
@@ -2097,6 +2125,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
}
}
end:
+ mutex_unlock(&fe->card->dpcm_mutex);
if (ret < 0)
dev_err(fe->dev, "ASoC: %s() failed at %s (%d)\n",
__func__, be->dai_link->name, ret);
@@ -2831,6 +2860,7 @@ struct snd_pcm_substream *
}
EXPORT_SYMBOL_GPL(snd_soc_dpcm_get_substream);
+/* This must be called with fe->card->dpcm_mutex held */
static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be,
int stream,
@@ -2842,7 +2872,6 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
int ret = 1;
int i;
- mutex_lock(&fe->card->dpcm_mutex);
for_each_dpcm_fe(be, stream, dpcm) {
if (dpcm->fe == fe)
@@ -2856,7 +2885,6 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
}
}
}
- mutex_unlock(&fe->card->dpcm_mutex);
/* it's safe to do this BE DAI */
return ret;
@@ -2865,6 +2893,7 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
/*
* We can only hw_free, stop, pause or suspend a BE DAI if any of it's FE
* are not running, paused or suspended for the specified stream direction.
+ * This must be called with fe->card->dpcm_mutex held.
*/
static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be, int stream)
@@ -2881,6 +2910,7 @@ static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
/*
* We can only change hw params a BE DAI if any of it's FE are not prepared,
* running, paused or suspended for the specified stream direction.
+ * This must be called with fe->card->dpcm_mutex held.
*/
static int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be, int stream)
--
2.25.1
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