linux-kernel - Re: [PATCH v3 03/11] iommufd: Introduce IOMMUFD_OBJ

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Message-ID: <CABQgh9Fea006HPwVTAuxk7KGh-7-YbjRhoUttVo_iACjAbr0CQ@mail.gmail.com>
Date: Wed, 16 Oct 2024 09:56:51 +0800
From: Zhangfei Gao <zhangfei.gao@...aro.org>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: jgg@...dia.com, kevin.tian@...el.com, will@...nel.org, joro@...tes.org, 
	suravee.suthikulpanit@....com, robin.murphy@....com, dwmw2@...radead.org, 
	baolu.lu@...ux.intel.com, shuah@...nel.org, linux-kernel@...r.kernel.org, 
	iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com, 
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com, 
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com, yi.l.liu@...el.com, 
	aik@....com, patches@...ts.linux.dev
Subject: Re: [PATCH v3 03/11] iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its
 related struct

On Wed, 16 Oct 2024 at 02:44, Nicolin Chen <nicolinc@...dia.com> wrote:
>
> On Mon, Oct 14, 2024 at 07:01:40PM -0700, Nicolin Chen wrote:
> > On Tue, Oct 15, 2024 at 09:15:01AM +0800, Zhangfei Gao wrote:
> >
> > > > > iommufd_device_bind
> > > > > iommufd_device_attach
> > > > > iommufd_vdevice_alloc_ioctl
> > > > >
> > > > > iommufd_device_detach
> > > > > iommufd_device_unbind // refcount check fail
> > > > > iommufd_vdevice_destroy ref--
> > > >
> > > > Things should be symmetric. As you suspected, vdevice should be
> > > > destroyed before iommufd_device_detach.
> > >
> > > I am trying based on your for_iommufd_viommu_p2-v3 branch, do you have
> > > this issue?
> > > In checking whether close fd before unbind?
> >
> > Oops, my bad. I will provide a fix.
>
> This should fix the problem:
>
> ---------------------------------------------------------------------
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 5fd3dd420290..13100cfea29d 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -277,6 +277,11 @@ EXPORT_SYMBOL_NS_GPL(iommufd_ctx_has_group, IOMMUFD);
>   */
>  void iommufd_device_unbind(struct iommufd_device *idev)
>  {
> +       mutex_lock(&idev->igroup->lock);
> +       /* idev->vdev object should be destroyed prior, yet just in case.. */
> +       if (idev->vdev)
> +               iommufd_object_remove(idev->ictx, NULL, idev->vdev->obj.id, 0);
> +       mutex_unlock(&idev->igroup->lock);
>         iommufd_object_destroy_user(idev->ictx, &idev->obj);
>  }
>  EXPORT_SYMBOL_NS_GPL(iommufd_device_unbind, IOMMUFD);
> ---------------------------------------------------------------------

Not yet
[  574.162112] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000004
[  574.261102] pc : iommufd_object_remove+0x7c/0x278
[  574.265795] lr : iommufd_device_unbind+0x44/0x98
in check

Thanks

>
> Thanks
> Nicolin