vhost: fix to check the return value of copy_to/from_user() correctly

copy_to/from_user() returns the number of bytes that could not be copied.

So we need to check if it is not zero, and in that case, we should return
the error number -EFAULT rather than directly return the return value from
copy_to/from_user().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -320,10 +320,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 {
 	struct vhost_memory mem, *newmem, *oldmem;
 	unsigned long size = offsetof(struct vhost_memory, regions);
-	long r;
-	r = copy_from_user(&mem, m, size);
-	if (r)
-		return r;
+	if (copy_from_user(&mem, m, size))
+		return -EFAULT;
 	if (mem.padding)
 		return -EOPNOTSUPP;
 	if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
@@ -333,11 +331,10 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 		return -ENOMEM;
 
 	memcpy(newmem, &mem, size);
-	r = copy_from_user(newmem->regions, m->regions,
-			   mem.nregions * sizeof *m->regions);
-	if (r) {
+	if (copy_from_user(newmem->regions, m->regions,
+			   mem.nregions * sizeof *m->regions)) {
 		kfree(newmem);
-		return r;
+		return -EFAULT;
 	}
 
 	if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL)))
@@ -389,9 +386,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 			r = -EBUSY;
 			break;
 		}
-		r = copy_from_user(&s, argp, sizeof s);
-		if (r < 0)
+		if (copy_from_user(&s, argp, sizeof s)) {
+			r = -EFAULT;
 			break;
+		}
 		if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
 			r = -EINVAL;
 			break;
@@ -405,9 +403,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 			r = -EBUSY;
 			break;
 		}
-		r = copy_from_user(&s, argp, sizeof s);
-		if (r < 0)
+		if (copy_from_user(&s, argp, sizeof s)) {
+			r = -EFAULT;
 			break;
+		}
 		if (s.num > 0xffff) {
 			r = -EINVAL;
 			break;
@@ -419,12 +418,14 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
 		s.num = vq->last_avail_idx;
-		r = copy_to_user(argp, &s, sizeof s);
+		if (copy_to_user(argp, &s, sizeof s))
+			r = -EFAULT;
 		break;
 	case VHOST_SET_VRING_ADDR:
-		r = copy_from_user(&a, argp, sizeof a);
-		if (r < 0)
+		if (copy_from_user(&a, argp, sizeof a)) {
+			r = -EFAULT;
 			break;
+		}
 		if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
 			r = -EOPNOTSUPP;
 			break;
@@ -477,9 +478,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 		vq->used = (void __user *)(unsigned long)a.used_user_addr;
 		break;
 	case VHOST_SET_VRING_KICK:
-		r = copy_from_user(&f, argp, sizeof f);
-		if (r < 0)
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
 			break;
+		}
 		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 		if (IS_ERR(eventfp)) {
 			r = PTR_ERR(eventfp);
@@ -492,9 +494,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 			filep = eventfp;
 		break;
 	case VHOST_SET_VRING_CALL:
-		r = copy_from_user(&f, argp, sizeof f);
-		if (r < 0)
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
 			break;
+		}
 		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 		if (IS_ERR(eventfp)) {
 			r = PTR_ERR(eventfp);
@@ -510,9 +513,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 			filep = eventfp;
 		break;
 	case VHOST_SET_VRING_ERR:
-		r = copy_from_user(&f, argp, sizeof f);
-		if (r < 0)
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
 			break;
+		}
 		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
 		if (IS_ERR(eventfp)) {
 			r = PTR_ERR(eventfp);
@@ -575,9 +579,10 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
 		r = vhost_set_memory(d, argp);
 		break;
 	case VHOST_SET_LOG_BASE:
-		r = copy_from_user(&p, argp, sizeof p);
-		if (r < 0)
+		if (copy_from_user(&p, argp, sizeof p)) {
+			r = -EFAULT;
 			break;
+		}
 		if ((u64)(unsigned long)p != p) {
 			r = -EFAULT;
 			break;