Message-ID: <20221114102729epcms2p75b469f77cdd41abab4148ffd438e8bd6@epcms2p7>
Date:   Mon, 14 Nov 2022 19:27:29 +0900
From:   Bongsu Jeon <bongsu.jeon@...sung.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        "leon@...nel.org" <leon@...nel.org>,
        Bongsu Jeon <bongsu.jeon@...sung.com>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "syzkaller@...glegroups.com" <syzkaller@...glegroups.com>
Subject: RE: [PATCH net-next v3] nfc: Allow to create multiple virtual nci
 devices

On Sat, Nov 5, 2022 at 2:04 AM Dmitry Vyukov<dvyukov@...gle.com> wrote:
> The current virtual nci driver is great for testing and fuzzing.
> But it allows to create at most one "global" device which does not allow
> to run parallel tests and harms fuzzing isolation and reproducibility.
> Restructure the driver to allow creation of multiple independent devices.
> This should be backwards compatible for existing tests.
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Bongsu Jeon <bongsu.jeon@...sung.com>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Cc: netdev@...r.kernel.org
> 
> ---
> Changes in v3:
>  - free vdev in virtual_ncidev_close()
> 
> Changes in v2:
>  - check return value of skb_clone()
>  - rebase onto currnet net-next
> ---
>  drivers/nfc/virtual_ncidev.c | 147 +++++++++++++++++------------------
>  1 file changed, 71 insertions(+), 76 deletions(-)
> 
> diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
> index 85c06dbb2c449..bb76c7c7cc822 100644
> --- a/drivers/nfc/virtual_ncidev.c
> +++ b/drivers/nfc/virtual_ncidev.c
> @@ -13,12 +13,6 @@
>  #include <linux/wait.h>
>  #include <net/nfc/nci_core.h>
>  
> -enum virtual_ncidev_mode {
> -	virtual_ncidev_enabled,
> -	virtual_ncidev_disabled,
> -	virtual_ncidev_disabling,
> -};
> -
>  #define IOCTL_GET_NCIDEV_IDX    0
>  #define VIRTUAL_NFC_PROTOCOLS	(NFC_PROTO_JEWEL_MASK | \
>  				 NFC_PROTO_MIFARE_MASK | \
> @@ -27,12 +21,12 @@ enum virtual_ncidev_mode {
>  				 NFC_PROTO_ISO14443_B_MASK | \
>  				 NFC_PROTO_ISO15693_MASK)
>  
> -static enum virtual_ncidev_mode state;
> -static DECLARE_WAIT_QUEUE_HEAD(wq);
> -static struct miscdevice miscdev;
> -static struct sk_buff *send_buff;
> -static struct nci_dev *ndev;
> -static DEFINE_MUTEX(nci_mutex);
> +struct virtual_nci_dev {
> +	struct nci_dev *ndev;
> +	struct mutex mtx;
> +	struct sk_buff *send_buff;
> +	struct wait_queue_head wq;
> +};
>  
>  static int virtual_nci_open(struct nci_dev *ndev)
>  {
> @@ -41,31 +35,34 @@ static int virtual_nci_open(struct nci_dev *ndev)
>  
>  static int virtual_nci_close(struct nci_dev *ndev)
>  {
> -	mutex_lock(&nci_mutex);
> -	kfree_skb(send_buff);
> -	send_buff = NULL;
> -	mutex_unlock(&nci_mutex);
> +	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
> +
> +	mutex_lock(&vdev->mtx);
> +	kfree_skb(vdev->send_buff);
> +	vdev->send_buff = NULL;
> +	mutex_unlock(&vdev->mtx);
>  
>  	return 0;
>  }
>  
>  static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
>  {
> -	mutex_lock(&nci_mutex);
> -	if (state != virtual_ncidev_enabled) {
> -		mutex_unlock(&nci_mutex);
> +	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
> +
> +	mutex_lock(&vdev->mtx);
> +	if (vdev->send_buff) {
> +		mutex_unlock(&vdev->mtx);
>  		kfree_skb(skb);
> -		return 0;
> +		return -1;
>  	}
> -
> -	if (send_buff) {
> -		mutex_unlock(&nci_mutex);
> +	vdev->send_buff = skb_copy(skb, GFP_KERNEL);
> +	if (!vdev->send_buff) {
> +		mutex_unlock(&vdev->mtx);
>  		kfree_skb(skb);
>  		return -1;
>  	}
> -	send_buff = skb_copy(skb, GFP_KERNEL);
> -	mutex_unlock(&nci_mutex);
> -	wake_up_interruptible(&wq);
> +	mutex_unlock(&vdev->mtx);
> +	wake_up_interruptible(&vdev->wq);
>  	consume_skb(skb);
>  
>  	return 0;
> @@ -80,29 +77,30 @@ static const struct nci_ops virtual_nci_ops = {
>  static ssize_t virtual_ncidev_read(struct file *file, char __user *buf,
>  				   size_t count, loff_t *ppos)
>  {
> +	struct virtual_nci_dev *vdev = file->private_data;
>  	size_t actual_len;
>  
> -	mutex_lock(&nci_mutex);
> -	while (!send_buff) {
> -		mutex_unlock(&nci_mutex);
> -		if (wait_event_interruptible(wq, send_buff))
> +	mutex_lock(&vdev->mtx);
> +	while (!vdev->send_buff) {
> +		mutex_unlock(&vdev->mtx);
> +		if (wait_event_interruptible(vdev->wq, vdev->send_buff))
>  			return -EFAULT;
> -		mutex_lock(&nci_mutex);
> +		mutex_lock(&vdev->mtx);
>  	}
>  
> -	actual_len = min_t(size_t, count, send_buff->len);
> +	actual_len = min_t(size_t, count, vdev->send_buff->len);
>  
> -	if (copy_to_user(buf, send_buff->data, actual_len)) {
> -		mutex_unlock(&nci_mutex);
> +	if (copy_to_user(buf, vdev->send_buff->data, actual_len)) {
> +		mutex_unlock(&vdev->mtx);
>  		return -EFAULT;
>  	}
>  
> -	skb_pull(send_buff, actual_len);
> -	if (send_buff->len == 0) {
> -		consume_skb(send_buff);
> -		send_buff = NULL;
> +	skb_pull(vdev->send_buff, actual_len);
> +	if (vdev->send_buff->len == 0) {
> +		consume_skb(vdev->send_buff);
> +		vdev->send_buff = NULL;
>  	}
> -	mutex_unlock(&nci_mutex);
> +	mutex_unlock(&vdev->mtx);
>  
>  	return actual_len;
>  }
> @@ -111,6 +109,7 @@ static ssize_t virtual_ncidev_write(struct file *file,
>  				    const char __user *buf,
>  				    size_t count, loff_t *ppos)
>  {
> +	struct virtual_nci_dev *vdev = file->private_data;
>  	struct sk_buff *skb;
>  
>  	skb = alloc_skb(count, GFP_KERNEL);
> @@ -122,63 +121,58 @@ static ssize_t virtual_ncidev_write(struct file *file,
>  		return -EFAULT;
>  	}
>  
> -	nci_recv_frame(ndev, skb);
> +	nci_recv_frame(vdev->ndev, skb);
>  	return count;
>  }
>  
>  static int virtual_ncidev_open(struct inode *inode, struct file *file)
>  {
>  	int ret = 0;
> +	struct virtual_nci_dev *vdev;
>  
> -	mutex_lock(&nci_mutex);
> -	if (state != virtual_ncidev_disabled) {
> -		mutex_unlock(&nci_mutex);
> -		return -EBUSY;
> -	}
> -
> -	ndev = nci_allocate_device(&virtual_nci_ops, VIRTUAL_NFC_PROTOCOLS,
> -				   0, 0);
> -	if (!ndev) {
> -		mutex_unlock(&nci_mutex);
> +	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
> +	if (!vdev)
> +		return -ENOMEM;
> +	vdev->ndev = nci_allocate_device(&virtual_nci_ops,
> +		VIRTUAL_NFC_PROTOCOLS, 0, 0);
> +	if (!vdev->ndev) {
> +		kfree(vdev);
>  		return -ENOMEM;
>  	}
>  
> -	ret = nci_register_device(ndev);
> +	mutex_init(&vdev->mtx);
> +	init_waitqueue_head(&vdev->wq);
> +	file->private_data = vdev;
> +	nci_set_drvdata(vdev->ndev, vdev);
> +
> +	ret = nci_register_device(vdev->ndev);
>  	if (ret < 0) {
> -		nci_free_device(ndev);
> -		mutex_unlock(&nci_mutex);
> +		nci_free_device(vdev->ndev);
> +		mutex_destroy(&vdev->mtx);
> +		kfree(vdev);
>  		return ret;
>  	}
> -	state = virtual_ncidev_enabled;
> -	mutex_unlock(&nci_mutex);
>  
>  	return 0;
>  }
>  
>  static int virtual_ncidev_close(struct inode *inode, struct file *file)
>  {
> -	mutex_lock(&nci_mutex);
> -
> -	if (state == virtual_ncidev_enabled) {
> -		state = virtual_ncidev_disabling;
> -		mutex_unlock(&nci_mutex);
> +	struct virtual_nci_dev *vdev = file->private_data;
>  
> -		nci_unregister_device(ndev);
> -		nci_free_device(ndev);
> -
> -		mutex_lock(&nci_mutex);
> -	}
> -
> -	state = virtual_ncidev_disabled;
> -	mutex_unlock(&nci_mutex);
> +	nci_unregister_device(vdev->ndev);
> +	nci_free_device(vdev->ndev);
> +	mutex_destroy(&vdev->mtx);
> +	kfree(vdev);
>  
>  	return 0;
>  }
>  
> -static long virtual_ncidev_ioctl(struct file *flip, unsigned int cmd,
> +static long virtual_ncidev_ioctl(struct file *file, unsigned int cmd,
>  				 unsigned long arg)
>  {
> -	const struct nfc_dev *nfc_dev = ndev->nfc_dev;
> +	struct virtual_nci_dev *vdev = file->private_data;
> +	const struct nfc_dev *nfc_dev = vdev->ndev->nfc_dev;
>  	void __user *p = (void __user *)arg;
>  
>  	if (cmd != IOCTL_GET_NCIDEV_IDX)
> @@ -199,14 +193,15 @@ static const struct file_operations virtual_ncidev_fops = {
>  	.unlocked_ioctl = virtual_ncidev_ioctl
>  };
>  
> +static struct miscdevice miscdev = {
> +	.minor = MISC_DYNAMIC_MINOR,
> +	.name = "virtual_nci",
> +	.fops = &virtual_ncidev_fops,
> +	.mode = 0600,
> +};
> +
>  static int __init virtual_ncidev_init(void)
>  {
> -	state = virtual_ncidev_disabled;
> -	miscdev.minor = MISC_DYNAMIC_MINOR;
> -	miscdev.name = "virtual_nci";
> -	miscdev.fops = &virtual_ncidev_fops;
> -	miscdev.mode = 0600;
> -
>  	return misc_register(&miscdev);
>  }
> 

Reviewed-by: Bongsu Jeon

Thanks for good design and improvement.

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