linux-kernel - Re: [PATCH] virtio-mmio: fix memory leak of vm

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Message-ID: <20230906100220.GA31628@dev-dsk-mheyne-1b-c1362c4d.eu-west-1.amazon.com>
Date:   Wed, 6 Sep 2023 10:02:20 +0000
From:   Maximilian Heyne <mheyne@...zon.de>
To:     <stable@...r.kernel.org>, "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio-mmio: fix memory leak of vm_dev

On Tue, Sep 05, 2023 at 09:42:28AM +0000, Maximilian Heyne wrote:
> With the recent removal of vm_dev from devres its memory is only freed
> via the callback virtio_mmio_release_dev. However, this only takes
> effect after device_add is called by register_virtio_device. Until then
> it's an unmanaged resource and must be explicitly freed on error exit.
> 
> This bug was discovered and resolved using Coverity Static Analysis
> Security Testing (SAST) by Synopsys, Inc.
> 
> Cc: stable@...r.kernel.org
> Fixes: 55c91fedd03d ("virtio-mmio: don't break lifecycle of vm_dev")
> Signed-off-by: Maximilian Heyne <mheyne@...zon.de>
> ---
> Please note that I have only compile tested this code.
> 
>  drivers/virtio/virtio_mmio.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 97760f611295..b2a48d07e973 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -631,13 +631,16 @@ static int virtio_mmio_probe(struct platform_device *pdev)
>  	spin_lock_init(&vm_dev->lock);
>  
>  	vm_dev->base = devm_platform_ioremap_resource(pdev, 0);
> -	if (IS_ERR(vm_dev->base))
> +	if (IS_ERR(vm_dev->base)) {
> +		kfree(vm_dev);
>  		return PTR_ERR(vm_dev->base);

I have a use-after-free here. Will send a v2 where this is fixed.

> +	}
>  
>  	/* Check magic value */
>  	magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);
>  	if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {
>  		dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!\n", magic);
> +		kfree(vm_dev);
>  		return -ENODEV;
>  	}
>  
> @@ -646,6 +649,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
>  	if (vm_dev->version < 1 || vm_dev->version > 2) {
>  		dev_err(&pdev->dev, "Version %ld not supported!\n",
>  				vm_dev->version);
> +		kfree(vm_dev);
>  		return -ENXIO;
>  	}
>  
> @@ -655,6 +659,7 @@ static int virtio_mmio_probe(struct platform_device *pdev)
>  		 * virtio-mmio device with an ID 0 is a (dummy) placeholder
>  		 * with no function. End probing now with no error reported.
>  		 */
> +		kfree(vm_dev);
>  		return -ENODEV;
>  	}
>  	vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
> -- 
> 2.40.1
> 



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