On Wed, Apr 11, 2018 at 10:35:41AM +0800, Stefan Hajnoczi wrote:
> 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 <torva...@linux-foundation.org>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>

Acked-by: Michael S. Tsirkin <m...@redhat.com>

> ---
>  drivers/vhost/vhost.h |  4 ++--
>  drivers/vhost/vhost.c | 66 
> +++++++++++++++++++++++++--------------------------
>  2 files changed, 35 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index d8ee85ae8fdc..6c844b90a168 100644
> --- a/drivers/vhost/vhost.h
> +++ b/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,
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index fc805b7fad9d..0fcb51a9940c 100644
> --- a/drivers/vhost/vhost.c
> +++ b/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);
>  }
> -- 
> 2.14.3
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