vhost: return bool from *_access_ok() functions

Currently vhost *_access_ok() functions return int.  This is error-prone
because there are two popular conventions:

1. 0 means failure, 1 means success
2. -errno means failure, 0 means success

Although vhost mostly uses #1, it does not do so consistently.
umem_access_ok() uses #2.

This patch changes the return type from int to bool so that false means
failure and true means success.  This eliminates a potential source of
errors.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/vhost/vhost.c

@@ -641,14 +641,14 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
 
-static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
+static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
 {
 	u64 a = addr / VHOST_PAGE_SIZE / 8;
 
 	/* Make sure 64 bit math will not overflow. */
 	if (a > ULONG_MAX - (unsigned long)log_base ||
 	    a + (unsigned long)log_base > ULONG_MAX)
-		return 0;
+		return false;
 
 	return access_ok(VERIFY_WRITE, log_base + a,
 			 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
@@ -661,30 +661,30 @@ static bool vhost_overflow(u64 uaddr, u64 size)
 }
 
 /* Caller should have vq mutex and device mutex. */
-static int vq_memory_access_ok(void __user *log_base, struct vhost_umem *umem,
-			       int log_all)
+static bool vq_memory_access_ok(void __user *log_base, struct vhost_umem *umem,
+				int log_all)
 {
 	struct vhost_umem_node *node;
 
 	if (!umem)
-		return 0;
+		return false;
 
 	list_for_each_entry(node, &umem->umem_list, link) {
 		unsigned long a = node->userspace_addr;
 
 		if (vhost_overflow(node->userspace_addr, node->size))
-			return 0;
+			return false;
 
 
 		if (!access_ok(VERIFY_WRITE, (void __user *)a,
 				    node->size))
-			return 0;
+			return false;
 		else if (log_all && !log_access_ok(log_base,
 						   node->start,
 						   node->size))
-			return 0;
+			return false;
 	}
-	return 1;
+	return true;
 }
 
 static inline void __user *vhost_vq_meta_fetch(struct vhost_virtqueue *vq,
@@ -701,13 +701,13 @@ static inline void __user *vhost_vq_meta_fetch(struct vhost_virtqueue *vq,
 
 /* Can we switch to this memory table? */
 /* Caller should have device mutex but not vq mutex */
-static int memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
-			    int log_all)
+static bool memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
+			     int log_all)
 {
 	int i;
 
 	for (i = 0; i < d->nvqs; ++i) {
-		int ok;
+		bool ok;
 		bool log;
 
 		mutex_lock(&d->vqs[i]->mutex);
@@ -717,12 +717,12 @@ static int memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
 			ok = vq_memory_access_ok(d->vqs[i]->log_base,
 						 umem, log);
 		else
-			ok = 1;
+			ok = true;
 		mutex_unlock(&d->vqs[i]->mutex);
 		if (!ok)
-			return 0;
+			return false;
 	}
-	return 1;
+	return true;
 }
 
 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
@@ -959,21 +959,21 @@ static void vhost_iotlb_notify_vq(struct vhost_dev *d,
 	spin_unlock(&d->iotlb_lock);
 }
 
-static int umem_access_ok(u64 uaddr, u64 size, int access)
+static bool umem_access_ok(u64 uaddr, u64 size, int access)
 {
 	unsigned long a = uaddr;
 
 	/* Make sure 64 bit math will not overflow. */
 	if (vhost_overflow(uaddr, size))
-		return -EFAULT;
+		return false;
 
 	if ((access & VHOST_ACCESS_RO) &&
 	    !access_ok(VERIFY_READ, (void __user *)a, size))
-		return -EFAULT;
+		return false;
 	if ((access & VHOST_ACCESS_WO) &&
 	    !access_ok(VERIFY_WRITE, (void __user *)a, size))
-		return -EFAULT;
-	return 0;
+		return false;
+	return true;
 }
 
 static int vhost_process_iotlb_msg(struct vhost_dev *dev,
@@ -988,7 +988,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
 			ret = -EFAULT;
 			break;
 		}
-		if (umem_access_ok(msg->uaddr, msg->size, msg->perm)) {
+		if (!umem_access_ok(msg->uaddr, msg->size, msg->perm)) {
 			ret = -EFAULT;
 			break;
 		}
@@ -1135,10 +1135,10 @@ static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova, int access)
 	return 0;
 }
 
-static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
-			struct vring_desc __user *desc,
-			struct vring_avail __user *avail,
-			struct vring_used __user *used)
+static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
+			 struct vring_desc __user *desc,
+			 struct vring_avail __user *avail,
+			 struct vring_used __user *used)
 
 {
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
@@ -1161,8 +1161,8 @@ static void vhost_vq_meta_update(struct vhost_virtqueue *vq,
 		vq->meta_iotlb[type] = node;
 }
 
-static int iotlb_access_ok(struct vhost_virtqueue *vq,
-			   int access, u64 addr, u64 len, int type)
+static bool iotlb_access_ok(struct vhost_virtqueue *vq,
+			    int access, u64 addr, u64 len, int type)
 {
 	const struct vhost_umem_node *node;
 	struct vhost_umem *umem = vq->iotlb;
@@ -1220,7 +1220,7 @@ EXPORT_SYMBOL_GPL(vq_iotlb_prefetch);
 
 /* Can we log writes? */
 /* Caller should have device mutex but not vq mutex */
-int vhost_log_access_ok(struct vhost_dev *dev)
+bool vhost_log_access_ok(struct vhost_dev *dev)
 {
 	return memory_access_ok(dev, dev->umem, 1);
 }
@@ -1228,8 +1228,8 @@ EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 
 /* Verify access for write logging. */
 /* Caller should have vq mutex and device mutex */
-static int vq_log_access_ok(struct vhost_virtqueue *vq,
-			    void __user *log_base)
+static bool vq_log_access_ok(struct vhost_virtqueue *vq,
+			     void __user *log_base)
 {
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
@@ -1242,14 +1242,14 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
 
 /* Can we start vq? */
 /* Caller should have vq mutex and device mutex */
-int vhost_vq_access_ok(struct vhost_virtqueue *vq)
+bool vhost_vq_access_ok(struct vhost_virtqueue *vq)
 {
 	if (!vq_log_access_ok(vq, vq->log_base))
-		return 0;
+		return false;
 
 	/* Access validation occurs at prefetch time with IOTLB */
 	if (vq->iotlb)
-		return 1;
+		return true;
 
 	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
 }

drivers/vhost/vhost.h

@@ -178,8 +178,8 @@ void vhost_dev_cleanup(struct vhost_dev *);
 void vhost_dev_stop(struct vhost_dev *);
 long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user *argp);
 long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp);
-int vhost_vq_access_ok(struct vhost_virtqueue *vq);
-int vhost_log_access_ok(struct vhost_dev *);
+bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
+bool vhost_log_access_ok(struct vhost_dev *);
 
 int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct iovec iov[], unsigned int iov_count,