On Sat, Aug 19, 2017 at 01:05:58PM +0100, Chris Wilson wrote:
> This is the same bug as we fixed in commit f6cd7daecff5 ("drm: Release
> driver references to handle before making it available again"), but now
> the exposure is via the PRIME lookup tables. If we remove the
> object/handle from the PRIME lut, then a new request for the same
> object/fd will generate a new handle, thus for a short window that
> object is known to userspace by two different handles. Fix this by
> releasing the driver tracking before PRIME.
>
> Fixes: 0ff926c7d4f0 ("drm/prime: add exported buffers to current fprivs
> imported buffer list (v2)")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Thierry Reding <treding@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Do we have an evil igt for this? I guess since the old one didn't have
one, this new race is also hard to reproduce ...
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/gpu/drm/drm_gem.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index ad4e9cfe48a2..88c6d78ee2d5 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -255,13 +255,13 @@ drm_gem_object_release_handle(int id, void *ptr, void *data)
> struct drm_gem_object *obj = ptr;
> struct drm_device *dev = obj->dev;
>
> + if (dev->driver->gem_close_object)
> + dev->driver->gem_close_object(obj, file_priv);
> +
> if (drm_core_check_feature(dev, DRIVER_PRIME))
> drm_gem_remove_prime_handles(obj, file_priv);
> drm_vma_node_revoke(&obj->vma_node, file_priv);
>
> - if (dev->driver->gem_close_object)
> - dev->driver->gem_close_object(obj, file_priv);
> -
> drm_gem_object_handle_put_unlocked(obj);
>
> return 0;
> --
> 2.14.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch