linux-kernel - Re: [PATCH v9 13/17] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa

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Message-ID: <20210713113114.GL1954@kadam>
Date:   Tue, 13 Jul 2021 14:31:14 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Xie Yongji <xieyongji@...edance.com>
Cc:     mst@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        sgarzare@...hat.com, parav@...dia.com, hch@...radead.org,
        christian.brauner@...onical.com, rdunlap@...radead.org,
        willy@...radead.org, viro@...iv.linux.org.uk, axboe@...nel.dk,
        bcrl@...ck.org, corbet@....net, mika.penttila@...tfour.com,
        joro@...tes.org, gregkh@...uxfoundation.org, zhe.he@...driver.com,
        xiaodong.liu@...el.com, songmuchun@...edance.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 13/17] vdpa: factor out vhost_vdpa_pa_map() and
 vhost_vdpa_pa_unmap()

On Tue, Jul 13, 2021 at 04:46:52PM +0800, Xie Yongji wrote:
> @@ -613,37 +618,28 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size)
>  	}
>  }
>  
> -static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> -					   struct vhost_iotlb_msg *msg)
> +static int vhost_vdpa_pa_map(struct vhost_vdpa *v,
> +			     u64 iova, u64 size, u64 uaddr, u32 perm)
>  {
>  	struct vhost_dev *dev = &v->vdev;
> -	struct vhost_iotlb *iotlb = dev->iotlb;
>  	struct page **page_list;
>  	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
>  	unsigned int gup_flags = FOLL_LONGTERM;
>  	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
>  	unsigned long lock_limit, sz2pin, nchunks, i;
> -	u64 iova = msg->iova;
> +	u64 start = iova;
>  	long pinned;
>  	int ret = 0;
>  
> -	if (msg->iova < v->range.first ||
> -	    msg->iova + msg->size - 1 > v->range.last)
> -		return -EINVAL;

This is not related to your patch, but can the "msg->iova + msg->size"
addition can have an integer overflow.  From looking at the callers it
seems like it can.  msg comes from:
  vhost_chr_write_iter()
  --> dev->msg_handler(dev, &msg);
      --> vhost_vdpa_process_iotlb_msg()
         --> vhost_vdpa_process_iotlb_update()

If I'm thinking of the right thing then these are allowed to overflow to
0 because of the " - 1" but not further than that.  I believe the check
needs to be something like:

	if (msg->iova < v->range.first ||
	    msg->iova - 1 > U64_MAX - msg->size ||
	    msg->iova + msg->size - 1 > v->range.last)

But writing integer overflow check correctly is notoriously difficult.
Do you think you could send a fix for that which is separate from the
patcheset?  We'd want to backport it to stable.

regards,
dan carpenter