linux-kernel - Re: stm class: Fix possible double free

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Date:   Thu, 18 Apr 2019 13:35:48 +0530
From:   Mukesh Ojha <mojha@...eaurora.org>
To:     Pan Bian <bianpan2016@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>
Cc:     linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: stm class: Fix possible double free


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@....com>


Looks good to me.
Reviewed-by: Mukesh Ojha <mojha@...eaurora.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;
>   }