Dne 06. 03. 19 v 9:46 KaiChieh Chuang napsal(a):

the dpcm get from fe_clients/be_clients may be free before use

possible race condition between void dpcm_be_disconnect( ... list_del(&dpcm->list_be); list_del(&dpcm->list_fe); kfree(dpcm); ...

and for_each_dpcm_fe() for_each_dpcm_be*()

race condition example Thread 1: snd_soc_dapm_mixer_update_power() -> soc_dpcm_runtime_update() -> dpcm_be_disconnect() -> kfree(dpcm); Thread 2: dpcm_fe_dai_trigger() -> dpcm_be_dai_trigger() -> snd_soc_dpcm_can_be_free_stop() -> if (dpcm->fe == fe)

Excpetion Scenario: two FE link to same BE FE1 -> BE FE2 ->

Thread 1: switch off mixer between FE2 -> BE Thread 2: pcm_stop FE1

Add a spin lock at snd_soc_card level, to protect the dpcm instance. The lock may be used in atomic context, so use spin lock.

Exception:

Unable to handle kernel paging request at virtual address dead0000000000e0

pc=<> [<ffffff8960e2cd10>] dpcm_be_dai_trigger+0x29c/0x47c sound/soc/soc-pcm.c:3226 if (dpcm->fe == fe) lr=<> [<ffffff8960e2f694>] dpcm_fe_dai_do_trigger+0x94/0x26c

Backtrace: [<ffffff89602dba80>] notify_die+0x68/0xb8 [<ffffff896028c7dc>] die+0x118/0x2a8 [<ffffff89602a2f84>] __do_kernel_fault+0x13c/0x14c [<ffffff89602a27f4>] do_translation_fault+0x64/0xa0 [<ffffff8960280cf8>] do_mem_abort+0x4c/0xd0 [<ffffff8960282ad0>] el1_da+0x24/0x40 [<ffffff8960e2cd10>] dpcm_be_dai_trigger+0x29c/0x47c [<ffffff8960e2f694>] dpcm_fe_dai_do_trigger+0x94/0x26c [<ffffff8960e2edec>] dpcm_fe_dai_trigger+0x3c/0x44 [<ffffff8960de5588>] snd_pcm_do_stop+0x50/0x5c [<ffffff8960dded24>] snd_pcm_action+0xb4/0x13c [<ffffff8960ddfdb4>] snd_pcm_drop+0xa0/0x128 [<ffffff8960de69bc>] snd_pcm_common_ioctl+0x9d8/0x30f0 [<ffffff8960de1cac>] snd_pcm_ioctl_compat+0x29c/0x2f14 [<ffffff89604c9d60>] compat_SyS_ioctl+0x128/0x244 [<ffffff8960283740>] el0_svc_naked+0x34/0x38 [<ffffffffffffffff>] 0xffffffffffffffff

Signed-off-by: KaiChieh Chuang kaichieh.chuang@mediatek.com

include/sound/soc.h | 2 ++ sound/soc/soc-core.c | 1 + sound/soc/soc-pcm.c | 31 ++++++++++++++++++++++++------- 3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h index eb7db605955b..1e2be35ed36f 100644 --- a/include/sound/soc.h +++ b/include/sound/soc.h @@ -1083,6 +1083,8 @@ struct snd_soc_card { struct mutex mutex; struct mutex dapm_mutex;

• spinlock_t dpcm_lock;
• bool instantiated; bool topology_shortname_created;

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c index 5a5764dba147..d88757659729 100644 --- a/sound/soc/soc-core.c +++ b/sound/soc/soc-core.c @@ -2820,6 +2820,7 @@ int snd_soc_register_card(struct snd_soc_card *card) card->instantiated = 0; mutex_init(&card->mutex); mutex_init(&card->dapm_mutex);

• spin_lock_init(&card->dpcm_lock);

  return snd_soc_bind_card(card);

} diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index a5b40e82dea4..f31eaf58e750 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -1294,9 +1294,11 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream) #ifdef CONFIG_DEBUG_FS debugfs_remove(dpcm->debugfs_state); #endif

• spin_lock(&fe->card->dpcm_lock);
  

  list_del(&dpcm->list_be); list_del(&dpcm->list_fe); kfree(dpcm);

• spin_unlock(&fe->card->dpcm_lock);
  

The unlock might be moved before kfree(). Also, I don't see the list_add() spin lock protection in your patch.

Jaroslav

} }

@@ -1548,9 +1550,11 @@ void dpcm_clear_pending_state(struct snd_soc_pcm_runtime *fe, int stream) { struct snd_soc_dpcm *dpcm;

• spin_lock(&fe->card->dpcm_lock); for_each_dpcm_be(fe, stream, dpcm) dpcm->be->dpcm[stream].runtime_update = SND_SOC_DPCM_UPDATE_NO;
• spin_unlock(&fe->card->dpcm_lock);

}

static void dpcm_be_dai_startup_unwind(struct snd_soc_pcm_runtime *fe, @@ -2640,11 +2644,13 @@ static int dpcm_run_update_startup(struct snd_soc_pcm_runtime *fe, int stream) dpcm_be_dai_shutdown(fe, stream); disconnect: /* disconnect any non started BEs */

• spin_lock(&fe->card->dpcm_lock); for_each_dpcm_be(fe, stream, dpcm) { struct snd_soc_pcm_runtime *be = dpcm->be; if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START) dpcm->state = SND_SOC_DPCM_LINK_STATE_FREE; }

• spin_unlock(&fe->card->dpcm_lock);

  return ret;

} @@ -3220,7 +3226,9 @@ int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe, { struct snd_soc_dpcm *dpcm; int state;

• int ret = 1;

• spin_lock(&fe->card->dpcm_lock); for_each_dpcm_fe(be, stream, dpcm) {

  if (dpcm->fe == fe)

@@ -3229,12 +3237,15 @@ int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe, state = dpcm->fe->dpcm[stream].state; if (state == SND_SOC_DPCM_STATE_START || state == SND_SOC_DPCM_STATE_PAUSED ||

• 	state == SND_SOC_DPCM_STATE_SUSPEND)
  

• 	return 0;
  

• 	state == SND_SOC_DPCM_STATE_SUSPEND) {
  

• 	ret = 0;
  

• 	break;
  

• }
  

  }

• spin_unlock(&fe->card->dpcm_lock);

  /* it's safe to free/stop this BE DAI */

• return 1;

• return ret;

} EXPORT_SYMBOL_GPL(snd_soc_dpcm_can_be_free_stop);

@@ -3247,7 +3258,9 @@ int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe, { struct snd_soc_dpcm *dpcm; int state;

• int ret = 1;

• spin_lock(&fe->card->dpcm_lock); for_each_dpcm_fe(be, stream, dpcm) {

  if (dpcm->fe == fe)

@@ -3257,12 +3270,15 @@ int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe, if (state == SND_SOC_DPCM_STATE_START || state == SND_SOC_DPCM_STATE_PAUSED || state == SND_SOC_DPCM_STATE_SUSPEND ||

• 	state == SND_SOC_DPCM_STATE_PREPARE)
  

• 	return 0;
  

• 	state == SND_SOC_DPCM_STATE_PREPARE) {
  

• 	ret = 0
  

• 	break;
  

• }
  

  }

• spin_unlock(&fe->card->dpcm_lock);

  /* it's safe to change hw_params */

• return 1;

• return ret;

} EXPORT_SYMBOL_GPL(snd_soc_dpcm_can_be_params);

@@ -3328,6 +3344,7 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe, goto out; }

• spin_lock(&fe->card->dpcm_lock); for_each_dpcm_be(fe, stream, dpcm) { struct snd_soc_pcm_runtime *be = dpcm->be; params = &dpcm->hw_params;

@@ -3348,7 +3365,7 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe, params_channels(params), params_rate(params)); }

• spin_unlock(&fe->card->dpcm_lock);

out: return offset; }