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@xxxxxxxxxxxx>
> ---
> 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;
> }
>
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
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