[alsa-devel] [RFC PATCH] ASoC: dpcm: prevent snd_soc_dpcm use after free
KaiChieh Chuang
kaichieh.chuang at mediatek.com
Wed Mar 6 09:01:13 CET 2019
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 of 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 at mediatek.com>
---
include/sound/soc.h | 2 ++
sound/soc/soc-core.c | 1 +
sound/soc/soc-pcm.c | 21 ++++++++++++++++++---
3 files changed, 21 insertions(+), 3 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..ac3f773ca768 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);
}
}
@@ -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;
}
@@ -3221,6 +3227,7 @@ int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
struct snd_soc_dpcm *dpcm;
int state;
+ spin_lock(&fe->card->dpcm_lock);
for_each_dpcm_fe(be, stream, dpcm) {
if (dpcm->fe == fe)
@@ -3229,9 +3236,12 @@ 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)
+ state == SND_SOC_DPCM_STATE_SUSPEND) {
+ spin_unlock(&fe->card->dpcm_lock);
return 0;
+ }
}
+ spin_unlock(&fe->card->dpcm_lock);
/* it's safe to free/stop this BE DAI */
return 1;
@@ -3248,6 +3258,7 @@ int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
struct snd_soc_dpcm *dpcm;
int state;
+ spin_lock(&fe->card->dpcm_lock);
for_each_dpcm_fe(be, stream, dpcm) {
if (dpcm->fe == fe)
@@ -3257,9 +3268,12 @@ 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)
+ state == SND_SOC_DPCM_STATE_PREPARE) {
+ spin_unlock(&fe->card->dpcm_lock);
return 0;
+ }
}
+ spin_unlock(&fe->card->dpcm_lock);
/* it's safe to change hw_params */
return 1;
@@ -3328,6 +3342,7 @@ 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 +3363,7 @@ 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;
}
--
2.18.0
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