[PATCH 0/3] Fix i2c mux module refcount issues

[PATCH 0/3] Fix i2c mux module refcount issues

[Herve Codina]

Hi,

Some i2c mux drivers wrongly use the pair of_find_i2c_adapter_by_node()
/ i2c_put_adapter() to lock the parent adapter.

Indeed, i2c_put_adapter() decrements the module refcount while
of_find_i2c_adapter_by_node() does not increment it. This leads to an
overflow over zero of the parent adapter user counter.

Identified mux drivers impacted are:
- i2c-mux-gpmux
- i2c-demux-pinctrl
- i2c-mux-pinctrl

Commit 48e9743dd648 ("i2c: core: add and export of_get_i2c_adapter_by_node()
interface") introduces of_get_i2c_adapter_by_node() to correctly handle
this refcount issue.

This series fixes the 3 identified mux drivers replacing the
of_find_i2c_adapter_by_node() call by an of_get_i2c_adapter_by_node()
call.

Best regards,
Hervé

Herve Codina (3):
  i2c: muxes: i2c-mux-pinctrl: Use of_get_i2c_adapter_by_node()
  i2c: muxes: i2c-demux-pinctrl: Use of_get_i2c_adapter_by_node()
  i2c: muxes: i2c-mux-gpmux: Use of_get_i2c_adapter_by_node()

 drivers/i2c/muxes/i2c-demux-pinctrl.c | 2 +-
 drivers/i2c/muxes/i2c-mux-gpmux.c     | 2 +-
 drivers/i2c/muxes/i2c-mux-pinctrl.c   | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

-- 
2.41.0

[PATCH 1/3] i2c: muxes: i2c-mux-pinctrl: Use of_get_i2c_adapter_by_node()

[Herve Codina]

i2c-mux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
i2c_put_adapter(). These pair alone is not correct to properly lock the
I2C parent adapter.

Indeed, i2c_put_adapter() decrements the module refcount while
of_find_i2c_adapter_by_node() does not increment it. This leads to an
overflow over zero of the parent adapter user counter.

Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
correctly the module refcount.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/i2c/muxes/i2c-mux-pinctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pinctrl.c b/drivers/i2c/muxes/i2c-mux-pinctrl.c
index 18236b9fa14a..6ebca7bfd8a2 100644
--- a/drivers/i2c/muxes/i2c-mux-pinctrl.c
+++ b/drivers/i2c/muxes/i2c-mux-pinctrl.c
@@ -62,7 +62,7 @@ static struct i2c_adapter *i2c_mux_pinctrl_parent_adapter(struct device *dev)
 		dev_err(dev, "Cannot parse i2c-parent\n");
 		return ERR_PTR(-ENODEV);
 	}
-	parent = of_find_i2c_adapter_by_node(parent_np);
+	parent = of_get_i2c_adapter_by_node(parent_np);
 	of_node_put(parent_np);
 	if (!parent)
 		return ERR_PTR(-EPROBE_DEFER);
-- 
2.41.0

Re: [PATCH 1/3] i2c: muxes: i2c-mux-pinctrl: Use of_get_i2c_adapter_by_node()

[Peter Rosin]

Hi!

2023-10-19 at 09:35, Herve Codina wrote:
> i2c-mux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
> i2c_put_adapter(). These pair alone is not correct to properly lock the
> I2C parent adapter.
> 
> Indeed, i2c_put_adapter() decrements the module refcount while
> of_find_i2c_adapter_by_node() does not increment it. This leads to an
> overflow over zero of the parent adapter user counter.

Perhaps "... underflow of the parent module refcount."?

> 
> Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Good find, and sorry about that!

Fixes: c4aee3e1b0de ("i2c: mux: pinctrl: remove platform_data")
Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
>  drivers/i2c/muxes/i2c-mux-pinctrl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-pinctrl.c b/drivers/i2c/muxes/i2c-mux-pinctrl.c
> index 18236b9fa14a..6ebca7bfd8a2 100644
> --- a/drivers/i2c/muxes/i2c-mux-pinctrl.c
> +++ b/drivers/i2c/muxes/i2c-mux-pinctrl.c
> @@ -62,7 +62,7 @@ static struct i2c_adapter *i2c_mux_pinctrl_parent_adapter(struct device *dev)
>  		dev_err(dev, "Cannot parse i2c-parent\n");
>  		return ERR_PTR(-ENODEV);
>  	}
> -	parent = of_find_i2c_adapter_by_node(parent_np);
> +	parent = of_get_i2c_adapter_by_node(parent_np);
>  	of_node_put(parent_np);
>  	if (!parent)
>  		return ERR_PTR(-EPROBE_DEFER);

Re: [PATCH 1/3] i2c: muxes: i2c-mux-pinctrl: Use of_get_i2c_adapter_by_node()

[Herve Codina]

Hi Peter,

On Thu, 19 Oct 2023 11:25:35 +0200
Peter Rosin <peda@axentia.se> wrote:

> Hi!
> 
> 2023-10-19 at 09:35, Herve Codina wrote:
> > i2c-mux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
> > i2c_put_adapter(). These pair alone is not correct to properly lock the
> > I2C parent adapter.
> > 
> > Indeed, i2c_put_adapter() decrements the module refcount while
> > of_find_i2c_adapter_by_node() does not increment it. This leads to an
> > overflow over zero of the parent adapter user counter.  
> 
> Perhaps "... underflow of the parent module refcount."?

Yes, will be changed in the next iteration.

> 
> > 
> > Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> > correctly the module refcount.
> > 
> > Signed-off-by: Herve Codina <herve.codina@bootlin.com>  
> 
> Good find, and sorry about that!
> 
> Fixes: c4aee3e1b0de ("i2c: mux: pinctrl: remove platform_data")
> Acked-by: Peter Rosin <peda@axentia.se>
> 
Will be added in the next iteration.

Thanks for the review,
Hervé

[PATCH 2/3] i2c: muxes: i2c-demux-pinctrl: Use of_get_i2c_adapter_by_node()

[Herve Codina]

i2c-demux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
i2c_put_adapter(). These pair alone is not correct to properly lock the
I2C parent adapter.

Indeed,	i2c_put_adapter() decrements the module refcount while
of_find_i2c_adapter_by_node() does not increment it. This leads to an
overflow over zero of the parent adapter user counter.

Use the	dedicated function, of_get_i2c_adapter_by_node(), to handle
correctly the module refcount.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/i2c/muxes/i2c-demux-pinctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
index 22f2280eab7f..9f2e4aa28159 100644
--- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
+++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
@@ -61,7 +61,7 @@ static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 ne
 	if (ret)
 		goto err;
 
-	adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
+	adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
 	if (!adap) {
 		ret = -ENODEV;
 		goto err_with_revert;
-- 
2.41.0

Re: [PATCH 2/3] i2c: muxes: i2c-demux-pinctrl: Use of_get_i2c_adapter_by_node()

[Peter Rosin]

Hi!

2023-10-19 at 09:35, Herve Codina wrote:
> i2c-demux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
> i2c_put_adapter(). These pair alone is not correct to properly lock the
> I2C parent adapter.
> 
> Indeed,	i2c_put_adapter() decrements the module refcount while
> of_find_i2c_adapter_by_node() does not increment it. This leads to an
> overflow over zero of the parent adapter user counter.

Perhaps "... underflow of the parent module refcount."?

> 
> Use the	dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Good find!

Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver")
Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
>  drivers/i2c/muxes/i2c-demux-pinctrl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> index 22f2280eab7f..9f2e4aa28159 100644
> --- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
> +++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
> @@ -61,7 +61,7 @@ static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 ne
>  	if (ret)
>  		goto err;
>  
> -	adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
> +	adap = of_get_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
>  	if (!adap) {
>  		ret = -ENODEV;
>  		goto err_with_revert;

Re: [PATCH 2/3] i2c: muxes: i2c-demux-pinctrl: Use of_get_i2c_adapter_by_node()

[Herve Codina]

Hi Peter,
On Thu, 19 Oct 2023 11:26:14 +0200
Peter Rosin <peda@axentia.se> wrote:

> Hi!
> 
> 2023-10-19 at 09:35, Herve Codina wrote:
> > i2c-demux-pinctrl uses the pair of_find_i2c_adapter_by_node() /
> > i2c_put_adapter(). These pair alone is not correct to properly lock the
> > I2C parent adapter.
> > 
> > Indeed,	i2c_put_adapter() decrements the module refcount while
> > of_find_i2c_adapter_by_node() does not increment it. This leads to an
> > overflow over zero of the parent adapter user counter.  
> 
> Perhaps "... underflow of the parent module refcount."?

Will be changed in the next iteration

> 
> > 
> > Use the	dedicated function, of_get_i2c_adapter_by_node(), to handle
> > correctly the module refcount.
> > 
> > Signed-off-by: Herve Codina <herve.codina@bootlin.com>  
> 
> Good find!
> 
> Fixes: 50a5ba876908 ("i2c: mux: demux-pinctrl: add driver")
> Acked-by: Peter Rosin <peda@axentia.se>
> 
Will be added in the next iteration.

Thanks for the review,
Hervé

[PATCH 3/3] i2c: muxes: i2c-mux-gpmux: Use of_get_i2c_adapter_by_node()

[Herve Codina]

i2c-mux-gpmux uses the pair of_find_i2c_adapter_by_node() /
i2c_put_adapter(). These pair alone is not correct to properly lock the
I2C parent adapter.

Indeed, i2c_put_adapter() decrements the module refcount while
of_find_i2c_adapter_by_node() does not increment it. This leads to an
overflow over zero of the parent adapter user counter.

Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
correctly the module refcount.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/i2c/muxes/i2c-mux-gpmux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/muxes/i2c-mux-gpmux.c b/drivers/i2c/muxes/i2c-mux-gpmux.c
index baccf4bfaf02..8305661e1253 100644
--- a/drivers/i2c/muxes/i2c-mux-gpmux.c
+++ b/drivers/i2c/muxes/i2c-mux-gpmux.c
@@ -52,7 +52,7 @@ static struct i2c_adapter *mux_parent_adapter(struct device *dev)
 		dev_err(dev, "Cannot parse i2c-parent\n");
 		return ERR_PTR(-ENODEV);
 	}
-	parent = of_find_i2c_adapter_by_node(parent_np);
+	parent = of_get_i2c_adapter_by_node(parent_np);
 	of_node_put(parent_np);
 	if (!parent)
 		return ERR_PTR(-EPROBE_DEFER);
-- 
2.41.0

Re: [PATCH 3/3] i2c: muxes: i2c-mux-gpmux: Use of_get_i2c_adapter_by_node()

[Peter Rosin]

Hi!

2023-10-19 at 09:35, Herve Codina wrote:
> i2c-mux-gpmux uses the pair of_find_i2c_adapter_by_node() /
> i2c_put_adapter(). These pair alone is not correct to properly lock the
> I2C parent adapter.
> 
> Indeed, i2c_put_adapter() decrements the module refcount while
> of_find_i2c_adapter_by_node() does not increment it. This leads to an
> overflow over zero of the parent adapter user counter.

Perhaps "... underflow of the parent module refcount."?

> 
> Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Good find, and sorry about that!

Fixes: ac8498f0ce53 ("i2c: i2c-mux-gpmux: new driver")
Acked-by: Peter Rosin <peda@axentia.se>

Cheers,
Peter

> ---
>  drivers/i2c/muxes/i2c-mux-gpmux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-gpmux.c b/drivers/i2c/muxes/i2c-mux-gpmux.c
> index baccf4bfaf02..8305661e1253 100644
> --- a/drivers/i2c/muxes/i2c-mux-gpmux.c
> +++ b/drivers/i2c/muxes/i2c-mux-gpmux.c
> @@ -52,7 +52,7 @@ static struct i2c_adapter *mux_parent_adapter(struct device *dev)
>  		dev_err(dev, "Cannot parse i2c-parent\n");
>  		return ERR_PTR(-ENODEV);
>  	}
> -	parent = of_find_i2c_adapter_by_node(parent_np);
> +	parent = of_get_i2c_adapter_by_node(parent_np);
>  	of_node_put(parent_np);
>  	if (!parent)
>  		return ERR_PTR(-EPROBE_DEFER);

Re: [PATCH 3/3] i2c: muxes: i2c-mux-gpmux: Use of_get_i2c_adapter_by_node()

[Herve Codina]

Hi Peter,

On Thu, 19 Oct 2023 11:26:41 +0200
Peter Rosin <peda@axentia.se> wrote:

> Hi!
> 
> 2023-10-19 at 09:35, Herve Codina wrote:
> > i2c-mux-gpmux uses the pair of_find_i2c_adapter_by_node() /
> > i2c_put_adapter(). These pair alone is not correct to properly lock the
> > I2C parent adapter.
> > 
> > Indeed, i2c_put_adapter() decrements the module refcount while
> > of_find_i2c_adapter_by_node() does not increment it. This leads to an
> > overflow over zero of the parent adapter user counter.  
> 
> Perhaps "... underflow of the parent module refcount."?

Yes, will be changed in the next iteration.

> 
> > 
> > Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> > correctly the module refcount.
> > 
> > Signed-off-by: Herve Codina <herve.codina@bootlin.com>  
> 
> Good find, and sorry about that!
> 
> Fixes: ac8498f0ce53 ("i2c: i2c-mux-gpmux: new driver")
> Acked-by: Peter Rosin <peda@axentia.se>

Will be added in the next iteration.

Thanks for the review,
Hervé