linux-kernel - Re: [RFC 2/4] vduse: Add file operation for mmap

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Message-ID: <8c1f1d67-4b81-f33d-bbc0-1c84ad05e183@redhat.com>
Date:   Tue, 11 Jul 2023 16:18:43 +0200
From:   Maxime Coquelin <maxime.coquelin@...hat.com>
To:     Cindy Lu <lulu@...hat.com>, jasowang@...hat.com, mst@...hat.com,
        xieyongji@...edance.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [RFC 2/4] vduse: Add file operation for mmap



On 6/28/23 08:59, Cindy Lu wrote:
> From: Your Name <you@...mple.com>
> 
> Add the operation for mmap, The user space APP will
> use this function to map the pages to userspace
> 
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
>   drivers/vdpa/vdpa_user/vduse_dev.c | 49 ++++++++++++++++++++++++++++++
>   1 file changed, 49 insertions(+)
> 
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index f845dc46b1db..1b833bf0ae37 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1313,6 +1313,54 @@ static struct vduse_dev *vduse_dev_get_from_minor(int minor)
>   	return dev;
>   }
>   
> +
> +static vm_fault_t vduse_vm_fault(struct vm_fault *vmf)
> +{
> +	struct vduse_dev *dev = vmf->vma->vm_file->private_data;
> +	struct vm_area_struct *vma = vmf->vma;
> +	u16 index = vma->vm_pgoff;
> +
> +	struct vdpa_reconnect_info *info;
> +	info = &dev->reconnect_info[index];
> +
> +	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +	if (remap_pfn_range(vma, vmf->address & PAGE_MASK, PFN_DOWN(info->addr),
> +			    PAGE_SIZE, vma->vm_page_prot))
> +		return VM_FAULT_SIGBUS;
> +	return VM_FAULT_NOPAGE;
> +}
> +
> +static const struct vm_operations_struct vduse_vm_ops = {
> +	.fault = vduse_vm_fault,
> +};
> +
> +static int vduse_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> +	struct vduse_dev *dev = file->private_data;
> +	struct vdpa_reconnect_info *info;
> +	unsigned long index = vma->vm_pgoff;
> +
> +	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
> +		return -EINVAL;
> +	if ((vma->vm_flags & VM_SHARED) == 0)
> +		return -EINVAL;
> +
> +	if (index > 65535)
> +		return -EINVAL;

You declare an array of 64 entries in patch 1, so it can overflow.

> +
> +	info = &dev->reconnect_info[index];
> +	if (info->addr & (PAGE_SIZE - 1))
> +		return -EINVAL;
> +	if (vma->vm_end - vma->vm_start != info->size) {
> +		return -ENOTSUPP;
> +	}
> +
> +	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
> +	vma->vm_ops = &vduse_vm_ops;
> +
> +	return 0;
> +}
> +
>   static int vduse_dev_open(struct inode *inode, struct file *file)
>   {
>   	int ret;
> @@ -1345,6 +1393,7 @@ static const struct file_operations vduse_dev_fops = {
>   	.unlocked_ioctl	= vduse_dev_ioctl,
>   	.compat_ioctl	= compat_ptr_ioctl,
>   	.llseek		= noop_llseek,
> +	.mmap		= vduse_mmap,
>   };
>   
>   static struct vduse_dev *vduse_dev_create(void)