Re: [PATCH v3] vduse: Fix off by one in vduse_dev_mmap()

[Michael S. Tsirkin]

On Wed, Feb 28, 2024 at 09:24:07PM +0300, Dan Carpenter wrote:
> The dev->vqs[] array has "dev->vq_num" elements.  It's allocated in
> vduse_dev_init_vqs().  Thus, this > comparison needs to be >= to avoid
> reading one element beyond the end of the array.
> 
> Add an array_index_nospec() as well to prevent speculation issues.
> 
> Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

Thanks a lot!
I assume this will be squashed in the relevant patch when that is
re-spun.

> ---
> v2: add array_index_nospec()
> v3: I accidentally corrupted v2.  Try again.
> 
>  drivers/vdpa/vdpa_user/vduse_dev.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index b7a1fb88c506..eb914084c650 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1532,9 +1532,10 @@ static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
>  	if ((vma->vm_flags & VM_SHARED) == 0)
>  		return -EINVAL;
>  
> -	if (index > dev->vq_num)
> +	if (index >= dev->vq_num)
>  		return -EINVAL;
>  
> +	index = array_index_nospec(index, dev->vq_num);
>  	vq = dev->vqs[index];
>  	vaddr = vq->vdpa_reconnect_vaddr;
>  	if (vaddr == 0)
> -- 
> 2.43.0