Received-SPF: pass (google.com: domain of linux-kernel+bounces-50724-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Fri, 2 Feb 2024 15:41:23 -0800
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Hamza Mahfooz <hamza.mahfooz@amd.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Alex Deucher <alexander.deucher@amd.com>,
	Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
	"Pan, Xinhui" <Xinhui.Pan@amd.com>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Mario Limonciello <mario.limonciello@amd.com>,
	Lijo Lazar <lijo.lazar@amd.com>,
	Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>,
	Le Ma <le.ma@amd.com>,
	=?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>,
	James Zhu <James.Zhu@amd.com>,
	Aurabindo Pillai <aurabindo.pillai@amd.com>,
	Alex Shi <alexs@kernel.org>, Jerry Snitselaar <jsnitsel@redhat.com>,
	Wei Liu <wei.liu@kernel.org>, Robin Murphy <robin.murphy@arm.com>,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-pci@vger.kernel.org
Subject: Re: [PATCH 3/3] drm/amdgpu: wire up the can_remove() callback
Message-ID: <2024020216-letdown-uproar-718d@gregkh>
References: <20240202222603.141240-1-hamza.mahfooz@amd.com>
 <20240202222603.141240-3-hamza.mahfooz@amd.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240202222603.141240-3-hamza.mahfooz@amd.com>

On Fri, Feb 02, 2024 at 05:25:56PM -0500, Hamza Mahfooz wrote:
> Removing an amdgpu device that still has user space references allocated
> to it causes undefined behaviour. So, implement amdgpu_pci_can_remove()
> and disallow devices that still have files allocated to them from being
> unbound.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index cc69005f5b46..cfa64f3c5be5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -2323,6 +2323,22 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
>  	return ret;
>  }
>  
> +static bool amdgpu_pci_can_remove(struct pci_dev *pdev)
> +{
> +	struct drm_device *dev = pci_get_drvdata(pdev);
> +
> +	mutex_lock(&dev->filelist_mutex);
> +
> +	if (!list_empty(&dev->filelist)) {
> +		mutex_unlock(&dev->filelist_mutex);
> +		return false;
> +	}
> +
> +	mutex_unlock(&dev->filelist_mutex);
> +
> +	return true;

Also, to be pedantic, this will not work as right after you returned
"true" here, userspace could open a file, causing the same issue you are
trying to prevent to have happen, happen.

So even if we wanted to do this, which again, we do not, this isn't even
a solution for it because it will still cause you problems.

greg k-h