linux-kernel - Re: [PATCH][next] vfio/mdpy: Fix memory leak of object mdev

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Message-ID: <20210622143926.7880e698.alex.williamson@redhat.com>
Date:   Tue, 22 Jun 2021 14:39:26 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     Colin King <colin.king@...onical.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kvm@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] vfio/mdpy: Fix memory leak of object
 mdev_state->vconfig

On Tue, 22 Jun 2021 15:58:24 -0300
Jason Gunthorpe <jgg@...pe.ca> wrote:

> On Tue, Jun 22, 2021 at 07:37:10PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> > 
> > In the case where the call to vfio_register_group_dev fails the error
> > return path kfree's mdev_state but not mdev_state->vconfig. Fix this
> > by kfree'ing mdev_state->vconfig before returning.
> > 
> > Addresses-Coverity: ("Resource leak")
> > Fixes: 437e41368c01 ("vfio/mdpy: Convert to use vfio_register_group_dev()")
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> >  samples/vfio-mdev/mdpy.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> > index 7e9c9df0f05b..393c9df6f6a0 100644
> > +++ b/samples/vfio-mdev/mdpy.c
> > @@ -261,6 +261,7 @@ static int mdpy_probe(struct mdev_device *mdev)
> >  
> >  	ret = vfio_register_group_dev(&mdev_state->vdev);
> >  	if (ret) {
> > +		kfree(mdev_state->vconfig);
> >  		kfree(mdev_state);
> >  		return ret;
> >  	}  
> 
> Thanks Colin, looks right
> 
> Alex, this is in your hch-mdev-direct-v4 branch can you squash or
> whatever?
> 
> Though if we are touching this I prefer the below:

Discrete fix above as a follow-up patch and later add the below as an
exit path cleanup, if you'd like to post it separately, seems like the
way to go to me.  Thanks,

Alex

> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 7e9c9df0f05bac..868a0e7fa90e98 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -235,17 +235,16 @@ static int mdpy_probe(struct mdev_device *mdev)
>  
>  	mdev_state->vconfig = kzalloc(MDPY_CONFIG_SPACE_SIZE, GFP_KERNEL);
>  	if (mdev_state->vconfig == NULL) {
> -		kfree(mdev_state);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto err_state;
>  	}
>  
>  	fbsize = roundup_pow_of_two(type->width * type->height * type->bytepp);
>  
>  	mdev_state->memblk = vmalloc_user(fbsize);
>  	if (!mdev_state->memblk) {
> -		kfree(mdev_state->vconfig);
> -		kfree(mdev_state);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto err_vconfig;
>  	}
>  	dev_info(dev, "%s: %s (%dx%d)\n", __func__, type->name, type->width,
>  		 type->height);
> @@ -260,12 +259,17 @@ static int mdpy_probe(struct mdev_device *mdev)
>  	mdpy_count++;
>  
>  	ret = vfio_register_group_dev(&mdev_state->vdev);
> -	if (ret) {
> -		kfree(mdev_state);
> -		return ret;
> -	}
> +	if (ret)
> +		goto err_vconfig;
> +
>  	dev_set_drvdata(&mdev->dev, mdev_state);
>  	return 0;
> +
> +err_vconfig:
> +	kfree(mdev_state->vconfig);
> +err_state:
> +	kfree(mdev_state);
> +	return ret;
>  }
>  
>  static void mdpy_remove(struct mdev_device *mdev)
>