Linux Virtualization - Jun 2020 - [PATCH] vhost_vdpa: Fix potential underflow in vhost_vdpa_mmap()

The "vma->vm_pgoff" variable is an unsigned long so if it's
larger than
INT_MAX then "index" can be negative leading to an underflow.  Fix
this
by changing the type of "index" to "unsigned long".

Fixes: ddd89d0a059d ("vhost_vdpa: support doorbell mapping via mmap")
Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
---
 drivers/vhost/vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 7580e34f76c10..a54b60d6623f0 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -818,7 +818,7 @@ static int vhost_vdpa_mmap(struct file *file, struct
vm_area_struct *vma)
 	struct vdpa_device *vdpa = v->vdpa;
 	const struct vdpa_config_ops *ops = vdpa->config;
 	struct vdpa_notification_area notify;
-	int index = vma->vm_pgoff;
+	unsigned long index = vma->vm_pgoff;
 
 	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
 		return -EINVAL;
-- 
2.26.2

On Wed, Jun 10, 2020 at 11:58:52AM +0300, Dan Carpenter
wrote:
> The "vma->vm_pgoff" variable is an unsigned long so if
it's larger than
> INT_MAX then "index" can be negative leading to an underflow. 
Fix this
> by changing the type of "index" to "unsigned long".
> 
> Fixes: ddd89d0a059d ("vhost_vdpa: support doorbell mapping via
mmap")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
Applied, thanks!
> ---
>  drivers/vhost/vdpa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 7580e34f76c10..a54b60d6623f0 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -818,7 +818,7 @@ static int vhost_vdpa_mmap(struct file *file, struct
vm_area_struct *vma)
>  	struct vdpa_device *vdpa = v->vdpa;
>  	const struct vdpa_config_ops *ops = vdpa->config;
>  	struct vdpa_notification_area notify;
> -	int index = vma->vm_pgoff;
> +	unsigned long index = vma->vm_pgoff;
>  
>  	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
>  		return -EINVAL;
> -- 
> 2.26.2