[PATCH v2] iio: dummy: iio_simple_dummy: check the return value of kstrdup()

[PATCH v2] iio: dummy: iio_simple_dummy: check the return value of kstrdup()

[xkernel.wang]

From: Xiaoke Wang <xkernel.wang@foxmail.com>

kstrdup() is also a memory allocation-related function, it return NULL
when some memory errors happen. So it is better to check the return
value of it so to catch the memory error in time. Besides, there should
have a kfree() to clear up the allocation if we get a failure later in
this function to prevent memory leak.

Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
---
Changelog:
1. Clean up some error labels(error_ret & error_kzalloc), directly make
them reflect what they are clearing up and return.
2. Clear up indio_dev->name on error path. I put that under label 
`error_free_device`, as kfree(NULL) is safe. Or I may need to add an
another label as the traget of `goto`.
Note: Suggestions are from Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
---
 drivers/iio/dummy/iio_simple_dummy.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/dummy/iio_simple_dummy.c b/drivers/iio/dummy/iio_simple_dummy.c
index c0b7ef9..430c12a 100644
--- a/drivers/iio/dummy/iio_simple_dummy.c
+++ b/drivers/iio/dummy/iio_simple_dummy.c
@@ -577,7 +577,7 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
 	swd = kzalloc(sizeof(*swd), GFP_KERNEL);
 	if (!swd) {
 		ret = -ENOMEM;
-		goto error_kzalloc;
+		return ERR_PTR(ret);
 	}
 	/*
 	 * Allocate an IIO device.
@@ -589,8 +589,9 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
 	 */
 	indio_dev = iio_device_alloc(parent, sizeof(*st));
 	if (!indio_dev) {
+		kfree(swd);
 		ret = -ENOMEM;
-		goto error_ret;
+		return ERR_PTR(ret);
 	}
 
 	st = iio_priv(indio_dev);
@@ -616,6 +617,10 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
 	 *    indio_dev->name = spi_get_device_id(spi)->name;
 	 */
 	indio_dev->name = kstrdup(name, GFP_KERNEL);
+	if (!indio_dev->name) {
+		ret = -ENOMEM;
+		goto error_free_device;
+	}
 
 	/* Provide description of available channels */
 	indio_dev->channels = iio_dummy_channels;
@@ -650,10 +655,9 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
 error_unregister_events:
 	iio_simple_dummy_events_unregister(indio_dev);
 error_free_device:
+	kfree(indio_dev->name);
 	iio_device_free(indio_dev);
-error_ret:
 	kfree(swd);
-error_kzalloc:
 	return ERR_PTR(ret);
 }
 
-- 

Re: [PATCH v2] iio: dummy: iio_simple_dummy: check the return value of kstrdup()

[Jonathan Cameron]

On Fri, 17 Dec 2021 11:48:28 +0800
xkernel.wang@foxmail.com wrote:

> From: Xiaoke Wang <xkernel.wang@foxmail.com>
> 
> kstrdup() is also a memory allocation-related function, it return NULL
> when some memory errors happen. So it is better to check the return
> value of it so to catch the memory error in time. Besides, there should
> have a kfree() to clear up the allocation if we get a failure later in
> this function to prevent memory leak.
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>

Hi a few minor follow on comments. Sorry it took me so long to get back to
you on this. I wasn't rushing as I won't be picking up fixes until the merge
window is done and I can rebase on rc1.

> ---
> Changelog:
> 1. Clean up some error labels(error_ret & error_kzalloc), directly make
> them reflect what they are clearing up and return.
> 2. Clear up indio_dev->name on error path. I put that under label 
> `error_free_device`, as kfree(NULL) is safe. Or I may need to add an
> another label as the traget of `goto`.
> Note: Suggestions are from Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
> ---
>  drivers/iio/dummy/iio_simple_dummy.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/dummy/iio_simple_dummy.c b/drivers/iio/dummy/iio_simple_dummy.c
> index c0b7ef9..430c12a 100644
> --- a/drivers/iio/dummy/iio_simple_dummy.c
> +++ b/drivers/iio/dummy/iio_simple_dummy.c
> @@ -577,7 +577,7 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
>  	swd = kzalloc(sizeof(*swd), GFP_KERNEL);
>  	if (!swd) {
>  		ret = -ENOMEM;
> -		goto error_kzalloc;
> +		return ERR_PTR(ret);

		return ERR_PTR(-ENOMEM);

>  	}
>  	/*
>  	 * Allocate an IIO device.
> @@ -589,8 +589,9 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
>  	 */
>  	indio_dev = iio_device_alloc(parent, sizeof(*st));
>  	if (!indio_dev) {
> +		kfree(swd);
Ah. Not what I meant unfortunately. This should look something like.

	if (!indio_dev) {
		ret = -ENOMEM;
		goto error_free_swd;
	}	
With error_ret label renamed to error_free_swd to reflect where it is.

>  		ret = -ENOMEM;
> -		goto error_ret;
> +		return ERR_PTR(ret);
>  	}
>  
>  	st = iio_priv(indio_dev);
> @@ -616,6 +617,10 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
>  	 *    indio_dev->name = spi_get_device_id(spi)->name;
>  	 */
>  	indio_dev->name = kstrdup(name, GFP_KERNEL);
> +	if (!indio_dev->name) {
> +		ret = -ENOMEM;
> +		goto error_free_device;
> +	}
>  
>  	/* Provide description of available channels */
>  	indio_dev->channels = iio_dummy_channels;
> @@ -650,10 +655,9 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
>  error_unregister_events:
>  	iio_simple_dummy_events_unregister(indio_dev);
>  error_free_device:
> +	kfree(indio_dev->name);
>  	iio_device_free(indio_dev);
> -error_ret:
>  	kfree(swd);
> -error_kzalloc:
>  	return ERR_PTR(ret);
>  }
>