linux-kernel - Re: [PATCH] vhost-vdpa: cleanup memory maps when closing vdpa fds

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Message-ID: <CACGkMEsOWmVGA1RYTNZybmzkz53g5cYEkJeMK_9uuQu-ezZcqg@mail.gmail.com>
Date:   Wed, 15 Feb 2023 10:56:46 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@...wei.com>
Cc:     mst@...hat.com, arei.gonglei@...wei.com, yechuan@...wei.com,
        huangzhichao@...wei.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] vhost-vdpa: cleanup memory maps when closing vdpa fds

On Wed, Feb 15, 2023 at 10:49 AM Longpeng (Mike, Cloud Infrastructure
Service Product Dept.) <longpeng2@...wei.com> wrote:
>
>
>
> 在 2023/2/15 10:00, Jason Wang 写道:
> > On Tue, Feb 14, 2023 at 2:28 PM Longpeng (Mike, Cloud Infrastructure
> > Service Product Dept.) <longpeng2@...wei.com> wrote:
> >>
> >>
> >>
> >> 在 2023/2/14 14:16, Jason Wang 写道:
> >>>
> >>> 在 2023/1/31 22:53, Longpeng(Mike) 写道:
> >>>> From: Longpeng <longpeng2@...wei.com>
> >>>>
> >>>> We must cleanup all memory maps when closing the vdpa fds, otherwise
> >>>> some critical resources (e.g. memory, iommu map) will leaked if the
> >>>> userspace exits unexpectedly (e.g. kill -9).
> >>>
> >>>
> >>> Sounds like a bug of the kernel, should we fix there?
> >>>
> >>
> >> For example, the iommu map is setup when QEMU calls VHOST_IOTLB_UPDATE
> >> ioctl and it'll be freed if QEMU calls VHOST_IOTLB_INVALIDATE ioctl.
> >>
> >> So maybe we release these resources in vdpa framework in kernel is a
> >> suitable choice?
> >
> > I think I need understand what does "resources" mean here:
> >
> > For iommu mapping, it should be freed by vhost_vdpa_free_domain() in
> > vhost_vdpa_release()?
> >
>
> Please consider the following lifecycle of the vdpa device:
>
> 1. vhost_vdpa_open
>      vhost_vdpa_alloc_domain
>
> 2. vhost_vdpa_pa_map
>      pin_user_pages
>      vhost_vdpa_map
>        iommu_map
>
> 3. kill QEMU
>
> 4. vhost_vdpa_release
>      vhost_vdpa_free_domain
>
> In this case, we have no opportunity to invoke unpin_user_pages or
> iommu_unmap to free the memory.

We do:

vhost_vdpa_cleanup()
    vhost_vdpa_remove_as()
        vhost_vdpa_iotlb_unmap()
            vhost_vdpa_pa_unmap()
                unpin_user_pages()
                vhost_vdpa_general_unmap()
                    iommu_unmap()
?

Btw, it looks like we should call vhost_vdpa_free_domain() *after*
vhost_vdpa_cleanup() otherwise it's a UAF?

Thanks

>
> > static int vhost_vdpa_release(struct inode *inode, struct file *filep)
> > {
> >          struct vhost_vdpa *v = filep->private_data;
> >          struct vhost_dev *d = &v->vdev;
> >
> >          mutex_lock(&d->mutex);
> >          filep->private_data = NULL;
> >          vhost_vdpa_clean_irq(v);
> >          vhost_vdpa_reset(v);
> >          vhost_dev_stop(&v->vdev);
> >          vhost_vdpa_free_domain(v);
> >          vhost_vdpa_config_put(v);
> >          vhost_vdpa_cleanup(v);
> >          mutex_unlock(&d->mutex);
> >
> >          atomic_dec(&v->opened);
> >          complete(&v->completion);
> >
> >          return 0;
> > }
> >
> >>
> >> By the way, Jason, can you reproduce the problem in your machine?
> >>
> >
> > Haven't got time in doing this but it should be the responsibility of
> > the author to validate this anyhow.
> >
> > Thanks
> >
> >>> Thanks
> >>>
> >>>
> >>>>
> >>>> Signed-off-by: Longpeng <longpeng2@...wei.com>
> >>>> ---
> >>>>    drivers/vhost/vdpa.c | 13 +++++++++++++
> >>>>    1 file changed, 13 insertions(+)
> >>>>
> >>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> >>>> index a527eeeac637..37477cffa5aa 100644
> >>>> --- a/drivers/vhost/vdpa.c
> >>>> +++ b/drivers/vhost/vdpa.c
> >>>> @@ -823,6 +823,18 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v,
> >>>>            vhost_vdpa_remove_as(v, asid);
> >>>>    }
> >>>> +static void vhost_vdpa_clean_map(struct vhost_vdpa *v)
> >>>> +{
> >>>> +    struct vhost_vdpa_as *as;
> >>>> +    u32 asid;
> >>>> +
> >>>> +    for (asid = 0; asid < v->vdpa->nas; asid++) {
> >>>> +        as = asid_to_as(v, asid);
> >>>> +        if (as)
> >>>> +            vhost_vdpa_unmap(v, &as->iotlb, 0ULL, 0ULL - 1);
> >>>> +    }
> >>>> +}
> >>>> +
> >>>>    static int vhost_vdpa_va_map(struct vhost_vdpa *v,
> >>>>                     struct vhost_iotlb *iotlb,
> >>>>                     u64 iova, u64 size, u64 uaddr, u32 perm)
> >>>> @@ -1247,6 +1259,7 @@ static int vhost_vdpa_release(struct inode
> >>>> *inode, struct file *filep)
> >>>>        vhost_vdpa_clean_irq(v);
> >>>>        vhost_vdpa_reset(v);
> >>>>        vhost_dev_stop(&v->vdev);
> >>>> +    vhost_vdpa_clean_map(v);
> >>>>        vhost_vdpa_free_domain(v);
> >>>>        vhost_vdpa_config_put(v);
> >>>>        vhost_vdpa_cleanup(v);
> >>>
> >>> .
> >>
> >
> > .
>