linux-kernel - Re: [PATCH 1/2] crypto/ccp: Cleanup misc_dev on sev

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Message-ID: <5bda6954-a4f1-117a-30ad-8b9737b835fa@amd.com>
Date:   Fri, 6 Mar 2020 09:56:12 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     John Allen <john.allen@....com>, linux-crypto@...r.kernel.org
Cc:     herbert@...dor.apana.org.au, davem@...emloft.net,
        brijesh.singh@....com, bp@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] crypto/ccp: Cleanup misc_dev on sev_exit()

On 3/3/20 7:57 AM, John Allen wrote:
> Explicitly free and clear misc_dev in sev_exit(). Since devm_kzalloc()
> associates misc_dev with the first device that gets probed, change from
> devm_kzalloc() to kzalloc() and explicitly free memory in sev_exit() as
> the first device probed is not guaranteed to be the last device released.
> To ensure that the variable gets properly set to NULL, remove the local
> definition of misc_dev.
> 
> Fixes: 200664d5237f ("crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support")
> Signed-off-by: John Allen <john.allen@....com>

Acked-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  drivers/crypto/ccp/sev-dev.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index e467860f797d..aa591dae067c 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -896,9 +896,9 @@ EXPORT_SYMBOL_GPL(sev_guest_df_flush);
>  
>  static void sev_exit(struct kref *ref)
>  {
> -	struct sev_misc_dev *misc_dev = container_of(ref, struct sev_misc_dev, refcount);
> -
>  	misc_deregister(&misc_dev->misc);
> +	kfree(misc_dev);
> +	misc_dev = NULL;
>  }
>  
>  static int sev_misc_init(struct sev_device *sev)
> @@ -916,7 +916,7 @@ static int sev_misc_init(struct sev_device *sev)
>  	if (!misc_dev) {
>  		struct miscdevice *misc;
>  
> -		misc_dev = devm_kzalloc(dev, sizeof(*misc_dev), GFP_KERNEL);
> +		misc_dev = kzalloc(sizeof(*misc_dev), GFP_KERNEL);
>  		if (!misc_dev)
>  			return -ENOMEM;
>  
>