stm class: Fix possible double free

stm class: Fix possible double free

[Pan Bian]

The function stm_register_device() calls put_device(&stm->dev) to
release allocated memory (in stm_device_release()) on error paths.
However, after that, the freed memory stm is released again, resulting
in a double free bug. There is a similar issue in the function
stm_source_register_device. This patch fixes these issues.

Signed-off-by: Pan Bian <bianpan2016@163.com>
---
 drivers/hwtracing/stm/core.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index c7ba8ac..cfb5c4d 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -886,8 +886,10 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 		return -ENOMEM;
 
 	stm->major = register_chrdev(0, stm_data->name, &stm_fops);
-	if (stm->major < 0)
-		goto err_free;
+	if (stm->major < 0) {
+		vfree(stm);
+		return err;
+	}
 
 	device_initialize(&stm->dev);
 	stm->dev.devt = MKDEV(stm->major, 0);
@@ -933,8 +935,6 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 
 	/* matches device_initialize() above */
 	put_device(&stm->dev);
-err_free:
-	vfree(stm);
 
 	return err;
 }
@@ -1277,7 +1277,6 @@ int stm_source_register_device(struct device *parent,
 
 err:
 	put_device(&src->dev);
-	kfree(src);
 
 	return err;
 }
-- 
2.7.4

Re: stm class: Fix possible double free

[Mukesh Ojha]

On 4/18/2019 12:52 PM, Pan Bian wrote:
> The function stm_register_device() calls put_device(&stm->dev) to
> release allocated memory (in stm_device_release()) on error paths.
> However, after that, the freed memory stm is released again, resulting
> in a double free bug. There is a similar issue in the function
> stm_source_register_device. This patch fixes these issues.
>
> Signed-off-by: Pan Bian <bianpan2016@163.com>


Looks good to me.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

Cheers,
-Mukesh

> ---
>   drivers/hwtracing/stm/core.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
> index c7ba8ac..cfb5c4d 100644
> --- a/drivers/hwtracing/stm/core.c
> +++ b/drivers/hwtracing/stm/core.c
> @@ -886,8 +886,10 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
>   		return -ENOMEM;
>   
>   	stm->major = register_chrdev(0, stm_data->name, &stm_fops);
> -	if (stm->major < 0)
> -		goto err_free;
> +	if (stm->major < 0) {
> +		vfree(stm);
> +		return err;
> +	}
>   
>   	device_initialize(&stm->dev);
>   	stm->dev.devt = MKDEV(stm->major, 0);
> @@ -933,8 +935,6 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
>   
>   	/* matches device_initialize() above */
>   	put_device(&stm->dev);
> -err_free:
> -	vfree(stm);
>   
>   	return err;
>   }
> @@ -1277,7 +1277,6 @@ int stm_source_register_device(struct device *parent,
>   
>   err:
>   	put_device(&src->dev);
> -	kfree(src);
>   
>   	return err;
>   }