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

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Message-ID: <CAJSP0QWW2QvibpcrZbcLzVp8ngnooiTqP8i2emd+0sdCj_7Yww@mail.gmail.com>
Date: Wed, 28 Feb 2024 14:19:34 -0500
From: Stefan Hajnoczi <stefanha@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Cindy Lu <lulu@...hat.com>, "Michael S. Tsirkin" <mst@...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, 28 Feb 2024 at 13:24, Dan Carpenter <dan.carpenter@...aro.org> 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>
> ---
> 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(-)

Reviewed-by: Stefan Hajnoczi <stefanha@...hat.com>

> 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
>
>