Re: [PATCH] device property: Fix usecount for of_graph_get_port_parent()

[Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>]

* Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> [170727 23:02]:
> * Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> [170727 15:19]:
> > On Thu, Jul 27, 2017 at 4:44 AM, Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> wrote:
> > > --- a/drivers/of/property.c
> > > +++ b/drivers/of/property.c
> > > @@ -708,6 +708,15 @@ struct device_node *of_graph_get_port_parent(struct device_node *node)
> > >  {
> > >         unsigned int depth;
> > >
> > > +       if (!node)
> > > +               return NULL;
> > > +
> > > +       /*
> > > +        * Preserve usecount for passed in node as of_get_next_parent()
> > > +        * will do of_node_put() on it.
> > > +        */
> > > +       of_node_get(node);
> > 
> > I think this messes up of_graph_get_remote_port_parent(). First it
> > calls of_graph_get_remote_endpoint which returns the endpoint node
> > with ref count incremented. Then you are incrementing it again here.
> 
> Hmm OK looks like I missed that one. If we want to have
> of_graph_get_port_parent not trash the node passed to it, we should
> just change things there too:

Found few more things to fix with git grep -C20 of_graph_get_port_parent,
below is v2.

Can you all prese review again and do some testing. I also fixed up
audio-graph-scu-card but can't test that one.

Regards,

Tony

8< ------
>From tony Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
Date: Thu, 27 Jul 2017 01:30:16 -0700
Subject: [PATCHv2] device property: Fix usecount for
 of_graph_get_port_parent()

Fix inconsistent use of of_graph_get_port_parent() where
asoc_simple_card_parse_graph_dai() does of_node_get() before
calling it while other callers do not. We can fix this by
not trashing the node passed to of_graph_get_port_parent().

Let's also make sure the callers have correct refcounts and remove
related incorrect of_node_put() calls for of_for_each_phandle
as that's done by of_phandle_iterator_next() except when
we break out of the loop early.

Let's fix both issues with a single patch to avoid kobject
refcounts getting messed up more if two patches are merged
separately.

Otherwise strange issues can happen caused by memory corruption
caused by too many kobject_del() calls such as:

BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:747
...
(___might_sleep)
(__mutex_lock)
(mutex_lock_nested)
(kernfs_remove)
(kobject_del)
(kobject_put)
(of_get_next_parent)
(of_graph_get_port_parent)
(asoc_simple_card_parse_graph_dai [snd_soc_simple_card_utils])
(asoc_graph_card_probe [snd_soc_audio_graph_card])

Fixes: 0ef472a973eb ("of_graph: add of_graph_get_port_parent()")
Fixes: 2692c1c63c29 ("ASoC: add audio-graph-card support")
Fixes: 1689333f8311 ("ASoC: simple-card-utils: add asoc_simple_card_parse_graph_dai()")
Cc: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Takashi Iwai <tiwai-IBi9RG/b67k@public.gmane.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org>
Cc: alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org
Signed-off-by: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
---
 drivers/of/property.c                    | 17 +++++++++++++++--
 sound/soc/generic/audio-graph-card.c     | 10 +++++-----
 sound/soc/generic/audio-graph-scu-card.c | 15 +++++++++------
 sound/soc/generic/simple-card-utils.c    |  8 +++-----
 sound/soc/soc-core.c                     |  2 ++
 5 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -708,6 +708,15 @@ struct device_node *of_graph_get_port_parent(struct device_node *node)
 {
 	unsigned int depth;
 
+	if (!node)
+		return NULL;
+
+	/*
+	 * Preserve usecount for passed in node as of_get_next_parent()
+	 * will do of_node_put() on it.
+	 */
+	of_node_get(node);
+
 	/* Walk 3 levels up only if there is 'ports' node. */
 	for (depth = 3; depth && node; depth--) {
 		node = of_get_next_parent(node);
@@ -728,12 +737,16 @@ EXPORT_SYMBOL(of_graph_get_port_parent);
 struct device_node *of_graph_get_remote_port_parent(
 			       const struct device_node *node)
 {
-	struct device_node *np;
+	struct device_node *np, *pp;
 
 	/* Get remote endpoint node. */
 	np = of_graph_get_remote_endpoint(node);
 
-	return of_graph_get_port_parent(np);
+	pp = of_graph_get_port_parent(np);
+
+	of_node_put(np);
+
+	return pp;
 }
 EXPORT_SYMBOL(of_graph_get_remote_port_parent);
 
diff --git a/sound/soc/generic/audio-graph-card.c b/sound/soc/generic/audio-graph-card.c
--- a/sound/soc/generic/audio-graph-card.c
+++ b/sound/soc/generic/audio-graph-card.c
@@ -224,9 +224,11 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
 
 	of_for_each_phandle(&it, rc, node, "dais", NULL, 0) {
 		ret = asoc_graph_card_dai_link_of(it.node, priv, idx++);
-		of_node_put(it.node);
-		if (ret < 0)
+		if (ret < 0) {
+			of_node_put(it.node);
+
 			return ret;
+		}
 	}
 
 	return asoc_simple_card_parse_card_name(card, NULL);
@@ -239,10 +241,8 @@ static int asoc_graph_get_dais_count(struct device *dev)
 	int count = 0;
 	int rc;
 
-	of_for_each_phandle(&it, rc, node, "dais", NULL, 0) {
+	of_for_each_phandle(&it, rc, node, "dais", NULL, 0)
 		count++;
-		of_node_put(it.node);
-	}
 
 	return count;
 }
diff --git a/sound/soc/generic/audio-graph-scu-card.c b/sound/soc/generic/audio-graph-scu-card.c
--- a/sound/soc/generic/audio-graph-scu-card.c
+++ b/sound/soc/generic/audio-graph-scu-card.c
@@ -215,7 +215,6 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
 		codec_ep = of_graph_get_remote_endpoint(cpu_ep);
 		rcpu_ep  = of_graph_get_remote_endpoint(codec_ep);
 
-		of_node_put(cpu_port);
 		of_node_put(cpu_ep);
 		of_node_put(codec_ep);
 		of_node_put(rcpu_ep);
@@ -232,8 +231,10 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
 
 		ret = asoc_simple_card_parse_daifmt(dev, cpu_ep, codec_ep,
 							    NULL, &daifmt);
-		if (ret < 0)
+		if (ret < 0) {
+			of_node_put(cpu_port);
 			goto parse_of_err;
+		}
 	}
 
 	dai_idx = 0;
@@ -250,7 +251,6 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
 			codec_ep = of_graph_get_remote_endpoint(cpu_ep);
 			codec_port = of_graph_get_port_parent(codec_ep);
 
-			of_node_put(cpu_port);
 			of_node_put(cpu_ep);
 			of_node_put(codec_ep);
 			of_node_put(codec_port);
@@ -266,13 +266,17 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
 
 				/* Back-End (= Codec) */
 				ret = asoc_graph_card_dai_link_of(codec_ep, priv, daifmt, dai_idx++, 0);
-				if (ret < 0)
+				if (ret < 0) {
+					of_node_put(cpu_port);
 					goto parse_of_err;
+				}
 			} else {
 				/* Front-End (= CPU) */
 				ret = asoc_graph_card_dai_link_of(cpu_ep, priv, daifmt, dai_idx++, 1);
-				if (ret < 0)
+				if (ret < 0) {
+					of_node_put(cpu_port);
 					goto parse_of_err;
+				}
 			}
 		}
 	}
@@ -306,7 +310,6 @@ static int asoc_graph_get_dais_count(struct device *dev)
 		codec_ep = of_graph_get_remote_endpoint(cpu_ep);
 		codec_port = of_graph_get_port_parent(codec_ep);
 
-		of_node_put(cpu_port);
 		of_node_put(cpu_ep);
 		of_node_put(codec_ep);
 		of_node_put(codec_port);
diff --git a/sound/soc/generic/simple-card-utils.c b/sound/soc/generic/simple-card-utils.c
--- a/sound/soc/generic/simple-card-utils.c
+++ b/sound/soc/generic/simple-card-utils.c
@@ -263,6 +263,9 @@ static int asoc_simple_card_get_dai_id(struct device_node *ep)
 			id = i;
 		i++;
 	}
+
+	of_node_put(node);
+
 	if (id < 0)
 		return -ENODEV;
 
@@ -282,11 +285,6 @@ int asoc_simple_card_parse_graph_dai(struct device_node *ep,
 	if (!dai_name)
 		return 0;
 
-	/*
-	 * of_graph_get_port_parent() will call
-	 * of_node_put(). So, call of_node_get() here
-	 */
-	of_node_get(ep);
 	node = of_graph_get_port_parent(ep);
 
 	/* Get dai->name */
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -4113,6 +4113,8 @@ int snd_soc_get_dai_id(struct device_node *ep)
 	}
 	mutex_unlock(&client_mutex);
 
+	of_node_put(node);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(snd_soc_get_dai_id);
-- 
2.13.2
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