NFC: nci: Allow to create multiple virtual nci devices

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@google.com>
Reviewed-by: Bongsu Jeon <bongsu.jeon@samsung.com>
Cc: Bongsu Jeon <bongsu.jeon@samsung.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20221115100017.787929-1-dvyukov@google.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

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);
 }