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drm: hold gem reference until object is no longer accessed 

A use-after-free in drm_gem_open_ioctl can happen if the
GEM object handle is closed between the idr lookup and
retrieving the size from said object since a local reference
is not being held at that point. Hold the local reference
while the object can still be accessed to fix this and
plug the potential security hole.

Signed-off-by: Steve Cohen <cohens@codeaurora.org>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1595284250-31580-1-git-send-email-cohens@codeaurora.org
zero-sugar-mainline-defconfig
Steve Cohen 2020-07-20 18:30:50 -04:00 committed by Daniel Vetter
parent 900ab59e26
commit 8490d6a7e0
1 changed files with 4 additions and 6 deletions
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10
drivers/gpu/drm/drm_gem.c
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@ -871,9 +871,6 @@ err:
* @file_priv: drm file-private structure
*
* Open an object using the global name, returning a handle and the size.
*
* This handle (of course) holds a reference to the object, so the object
* will not go away until the handle is deleted.
*/
int
drm_gem_open_ioctl(struct drm_device *dev, void *data,
@ -898,14 +895,15 @@ drm_gem_open_ioctl(struct drm_device *dev, void *data,
/* drm_gem_handle_create_tail unlocks dev->object_name_lock. */
ret = drm_gem_handle_create_tail(file_priv, obj, &handle);
drm_gem_object_put_unlocked(obj);
if (ret)
return ret;
goto err;
args->handle = handle;
args->size = obj->size;
return 0;
err:
drm_gem_object_put_unlocked(obj);
return ret;
}
/**