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SubjectRe: [PATCH 5/6] vduse: Support registering userspace memory for IOTLB
On Wed, Jun 29, 2022 at 04:25:40PM +0800, Xie Yongji wrote:
> Introduce two ioctls: VDUSE_IOTLB_REG_UMEM and
> VDUSE_IOTLB_DEREG_UMEM to support registering
> and de-registering userspace memory for IOTLB
> in virtio-vdpa case.
>
> Now it only supports registering userspace memory
> for IOTLB as bounce buffer.
>
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 138 +++++++++++++++++++++++++++++
> include/uapi/linux/vduse.h | 28 ++++++
> 2 files changed, 166 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index c47a5d9765cf..7b2ea7612da9 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -21,6 +21,7 @@
> #include <linux/uio.h>
> #include <linux/vdpa.h>
> #include <linux/nospec.h>
> +#include <linux/sched/mm.h>
> #include <uapi/linux/vduse.h>
> #include <uapi/linux/vdpa.h>
> #include <uapi/linux/virtio_config.h>
> @@ -64,6 +65,13 @@ struct vduse_vdpa {
> struct vduse_dev *dev;
> };
>
> +struct vduse_iotlb_mem {
> + unsigned long iova;
> + unsigned long npages;
> + struct page **pages;
> + struct mm_struct *mm;
> +};
> +
> struct vduse_dev {
> struct vduse_vdpa *vdev;
> struct device *dev;
> @@ -95,6 +103,8 @@ struct vduse_dev {
> u8 status;
> u32 vq_num;
> u32 vq_align;
> + struct vduse_iotlb_mem *iotlb_mem;
> + struct mutex mem_lock;
> };
>
> struct vduse_dev_msg {
> @@ -917,6 +927,100 @@ static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
> return ret;
> }
>
> +static int vduse_dev_dereg_iotlb_mem(struct vduse_dev *dev,
> + u64 iova, u64 size)
> +{
> + int ret;
> +
> + mutex_lock(&dev->mem_lock);
> + ret = -ENOENT;
> + if (!dev->iotlb_mem)
> + goto unlock;
> +
> + ret = -EINVAL;
> + if (dev->iotlb_mem->iova != iova || size != dev->domain->bounce_size)
> + goto unlock;
> +
> + vduse_domain_remove_user_bounce_pages(dev->domain);
> + unpin_user_pages(dev->iotlb_mem->pages, dev->iotlb_mem->npages);

I notice you don't mark the pages dirty. This is going to be a problem.

> + atomic64_sub(dev->iotlb_mem->npages, &dev->iotlb_mem->mm->pinned_vm);
> + mmdrop(dev->iotlb_mem->mm);
> + vfree(dev->iotlb_mem->pages);
> + kfree(dev->iotlb_mem);
> + dev->iotlb_mem = NULL;
> + ret = 0;
> +unlock:
> + mutex_unlock(&dev->mem_lock);
> + return ret;
> +}
> +
> +static int vduse_dev_reg_iotlb_mem(struct vduse_dev *dev,
> + u64 iova, u64 uaddr, u64 size)
> +{
> + struct page **page_list = NULL;
> + struct vduse_iotlb_mem *mem = NULL;
> + long pinned = 0;
> + unsigned long npages, lock_limit;
> + int ret;
> +
> + if (size != dev->domain->bounce_size ||
> + iova != 0 || uaddr & ~PAGE_MASK)
> + return -EINVAL;
> +
> + mutex_lock(&dev->mem_lock);
> + ret = -EEXIST;
> + if (dev->iotlb_mem)
> + goto unlock;
> +
> + ret = -ENOMEM;
> + npages = size >> PAGE_SHIFT;
> + page_list = vmalloc(array_size(npages,
> + sizeof(struct page *)));

Is this basically trying to do a vmalloc with userspace-controlled size?
That's an easy DOS vector.

> + mem = kzalloc(sizeof(*mem), GFP_KERNEL);
> + if (!page_list || !mem)
> + goto unlock;
> +
> + mmap_read_lock(current->mm);
> +
> + lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK));
> + if (npages + atomic64_read(&current->mm->pinned_vm) > lock_limit)
> + goto out;
> +
> + pinned = pin_user_pages(uaddr, npages, FOLL_LONGTERM | FOLL_WRITE,
> + page_list, NULL);
> + if (pinned != npages) {
> + ret = pinned < 0 ? pinned : -ENOMEM;
> + goto out;
> + }


This is a popular approach but it's problematic if multiple
devices try to pin the same page.
Can this happen here?

> +
> + ret = vduse_domain_add_user_bounce_pages(dev->domain,
> + page_list, pinned);
> + if (ret)
> + goto out;
> +
> + atomic64_add(npages, &current->mm->pinned_vm);
> +
> + mem->pages = page_list;
> + mem->npages = pinned;
> + mem->iova = iova;
> + mem->mm = current->mm;
> + mmgrab(current->mm);
> +
> + dev->iotlb_mem = mem;
> +out:
> + if (ret && pinned > 0)
> + unpin_user_pages(page_list, pinned);
> +
> + mmap_read_unlock(current->mm);
> +unlock:
> + if (ret) {
> + vfree(page_list);
> + kfree(mem);
> + }
> + mutex_unlock(&dev->mem_lock);
> + return ret;
> +}
> +
> static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> @@ -943,6 +1047,16 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (entry.start > entry.last)
> break;
>
> + if (domain->bounce_map && dev->iotlb_mem) {
> + ret = -EEXIST;
> + if (entry.start >= 0 &&
> + entry.last < domain->bounce_size)
> + break;
> +
> + if (entry.start < domain->bounce_size)
> + entry.start = domain->bounce_size;
> + }
> +
> spin_lock(&domain->iotlb_lock);
> map = vhost_iotlb_itree_first(domain->iotlb,
> entry.start, entry.last);
> @@ -1102,6 +1216,28 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> ret = 0;
> break;
> }
> + case VDUSE_IOTLB_REG_UMEM: {
> + struct vduse_iotlb_umem umem;
> +
> + ret = -EFAULT;
> + if (copy_from_user(&umem, argp, sizeof(umem)))
> + break;
> +
> + ret = vduse_dev_reg_iotlb_mem(dev, umem.iova,
> + umem.uaddr, umem.size);
> + break;
> + }
> + case VDUSE_IOTLB_DEREG_UMEM: {
> + struct vduse_iotlb_umem umem;
> +
> + ret = -EFAULT;
> + if (copy_from_user(&umem, argp, sizeof(umem)))
> + break;
> +
> + ret = vduse_dev_dereg_iotlb_mem(dev, umem.iova,
> + umem.size);
> + break;
> + }
> default:
> ret = -ENOIOCTLCMD;
> break;
> @@ -1114,6 +1250,7 @@ static int vduse_dev_release(struct inode *inode, struct file *file)
> {
> struct vduse_dev *dev = file->private_data;
>
> + vduse_dev_dereg_iotlb_mem(dev, 0, dev->domain->bounce_size);
> spin_lock(&dev->msg_lock);
> /* Make sure the inflight messages can processed after reconncection */
> list_splice_init(&dev->recv_list, &dev->send_list);
> @@ -1176,6 +1313,7 @@ static struct vduse_dev *vduse_dev_create(void)
> return NULL;
>
> mutex_init(&dev->lock);
> + mutex_init(&dev->mem_lock);
> spin_lock_init(&dev->msg_lock);
> INIT_LIST_HEAD(&dev->send_list);
> INIT_LIST_HEAD(&dev->recv_list);
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index c201b7a77c2c..1b17391e228f 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -227,6 +227,34 @@ struct vduse_iotlb_info {
> /* Get IOTLB information, e.g. bounce buffer size */
> #define VDUSE_IOTLB_GET_INFO _IOR(VDUSE_BASE, 0x18, struct vduse_iotlb_info)
>
> +/**
> + * struct vduse_iotlb_umem - userspace memory configuration
> + * @uaddr: start address of userspace memory, it must be aligned to page size
> + * @iova: IOVA of userspace memory, it must be equal to bounce iova returned
> + * by VDUSE_IOTLB_GET_INFO now
> + * @size: size of userspace memory, it must be equal to bounce size returned
> + * by VDUSE_IOTLB_GET_INFO now
> + * @reserved: for future use, needs to be initialized to zero

You should check that it's 0 in that case, otherwise userspace
will conveniently forget.

> + *
> + * Structure used by VDUSE_IOTLB_REG_UMEM and VDUSE_IOTLB_DEREG_UMEM
> + * ioctls to register/de-register userspace memory for IOTLB.
> + */
> +struct vduse_iotlb_umem {
> + __u64 uaddr;
> + __u64 iova;
> + __u64 size;
> + __u64 reserved[3];
> +};
> +
> +/*
> + * Register userspace memory for IOTLB. Now we only support registering
> + * userspace memory as bounce buffer.
> + */
> +#define VDUSE_IOTLB_REG_UMEM _IOW(VDUSE_BASE, 0x19, struct vduse_iotlb_umem)
> +
> +/* De-register the userspace memory. Caller should set iova and size field. */
> +#define VDUSE_IOTLB_DEREG_UMEM _IOW(VDUSE_BASE, 0x1a, struct vduse_iotlb_umem)
> +
> /* The control messages definition for read(2)/write(2) on /dev/vduse/$NAME */
>
> /**
> --
> 2.20.1

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