linux-kernel - Re: [PATCH v3] vduse: Fix off by one in vduse_dev

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Date: Tue, 19 Mar 2024 03:23:00 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Cindy Lu <lulu@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Xie Yongji <xieyongji@...edance.com>,
	Maxime Coquelin <maxime.coquelin@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Christian Brauner <brauner@...nel.org>,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v3] vduse: Fix off by one in vduse_dev_mmap()

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@...aro.org>

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