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Subject: Re: [PATCH v9 13/17] vdpa: factor out vhost_vdpa_pa_map() and
 vhost_vdpa_pa_unmap()
To:     Dan Carpenter <dan.carpenter@oracle.com>,
        Xie Yongji <xieyongji@bytedance.com>
Cc:     mst@redhat.com, stefanha@redhat.com, sgarzare@redhat.com,
        parav@nvidia.com, hch@infradead.org,
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        willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk,
        bcrl@kvack.org, corbet@lwn.net, mika.penttila@nextfour.com,
        joro@8bytes.org, gregkh@linuxfoundation.org, zhe.he@windriver.com,
        xiaodong.liu@intel.com, songmuchun@bytedance.com,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
References: <20210713084656.232-1-xieyongji@bytedance.com>
 <20210713084656.232-14-xieyongji@bytedance.com> <20210713113114.GL1954@kadam>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <20e75b53-0dce-2f2d-b717-f78553bddcd8@redhat.com>
Date:   Wed, 14 Jul 2021 10:14:32 +0800
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?? 2021/7/13 ????7:31, Dan Carpenter д??:
> 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()


Yes.


>
> 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 ||


I guess we don't need - 1 here?

Thanks


> 	    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
>