[1/2] drm/i915: Use drm_dev_unplug()

Submitted by Janusz Krzysztofik on April 5, 2019, 1:02 p.m.

Details

Message ID 20190405130235.7707-2-janusz.krzysztofik@linux.intel.com
State New
Headers show
Series "Stop users from using the device on driver unbind" ( rev: 1 ) in Intel GFX

Browsing this patch as part of:
"Stop users from using the device on driver unbind" rev 1 in Intel GFX
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Commit Message

Janusz Krzysztofik April 5, 2019, 1:02 p.m.
From: Janusz Krzysztofik <janusz.krzysztofik@intel.com>

The driver does not currently support unbinding from a device which is
in use.  Since open file descriptors may still be pointing into kernel
memory where the device structures used to be, entirely correct kernel
panics protect the driver from being unbound as we should not be
unbinding it before those dangling pointers have been made safe.

According to the documentation found inside drivers/gpu/drm/drm_drv.c,
drm_dev_unplug() should be used instead of drm_dev_unregister() in
order to make a device inaccessible to users as soon as it is unpluged.
Follow that advice to make those possibly dangling pointers safe,
protected by DRM layer from a user who is otherwise left pointing into
possibly reused kernel memory after the driver has been unbound from
the device.  Once done, also cancel inflight operations immediately by
calling i915_gem_set_wedged().

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 9df65d386d11..66163378c481 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1596,7 +1596,7 @@  static void i915_driver_unregister(struct drm_i915_private *dev_priv)
 	i915_pmu_unregister(dev_priv);
 
 	i915_teardown_sysfs(dev_priv);
-	drm_dev_unregister(&dev_priv->drm);
+	drm_dev_unplug(&dev_priv->drm);
 
 	i915_gem_shrinker_unregister(dev_priv);
 }

Comments

On Fri, Apr 05, 2019 at 03:02:34PM +0200, Janusz Krzysztofik wrote:
> From: Janusz Krzysztofik <janusz.krzysztofik@intel.com>
> 
> The driver does not currently support unbinding from a device which is
> in use.  Since open file descriptors may still be pointing into kernel
> memory where the device structures used to be, entirely correct kernel
> panics protect the driver from being unbound as we should not be
> unbinding it before those dangling pointers have been made safe.
> 
> According to the documentation found inside drivers/gpu/drm/drm_drv.c,
> drm_dev_unplug() should be used instead of drm_dev_unregister() in
> order to make a device inaccessible to users as soon as it is unpluged.
> Follow that advice to make those possibly dangling pointers safe,
> protected by DRM layer from a user who is otherwise left pointing into
> possibly reused kernel memory after the driver has been unbound from
> the device.  Once done, also cancel inflight operations immediately by
> calling i915_gem_set_wedged().
> 
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/i915/i915_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 9df65d386d11..66163378c481 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1596,7 +1596,7 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
>  	i915_pmu_unregister(dev_priv);
>  
>  	i915_teardown_sysfs(dev_priv);
> -	drm_dev_unregister(&dev_priv->drm);
> +	drm_dev_unplug(&dev_priv->drm);
>  
>  	i915_gem_shrinker_unregister(dev_priv);
>  }
> -- 
> 2.20.1
>
Use drm_dev_unplug() to have device resources protected from user access
by DRM layer as soon as the driver is going to be unbound.

Janusz Krzysztofik (1):
  drm/i915: Use drm_dev_unplug()

 drivers/gpu/drm/i915/i915_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Since this patch should be now safe for use if merged with current
drm-next or drm-tip branch which no longer suffer from incorrectly
resolved merge confilct that was breaking it, finally fixed by commit
bd53280ef042 ("drm/drv: Fix incorrect resolution of merge conflict"),
I'm resending it with Daniel's Reviewed-by: added.

Former patch 2/2 has been dropped as it is already in drm-intel-next as
commit 141f3767e7b8 ("drm/i915: Mark GEM wedged right after marking
device unplugged").  BTW, the wersion I sent was screwed up, not
reflecting Chris' intention precisely enough, but Chris was vigilant and
fixed it.  Sorry Chris.

Thanks,
Janusz