| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 009/149] drm: hold gem reference until object is no longer accessed | Date | Thu, 20 Aug 2020 11:21:26 +0200 |
| |
From: Steve Cohen <cohens@codeaurora.org>
commit 8490d6a7e0a0a6fab5c2d82d57a3937306660864 upstream.
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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/gpu/drm/drm_gem.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
--- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -652,9 +652,6 @@ 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, @@ -679,14 +676,15 @@ drm_gem_open_ioctl(struct drm_device *de /* drm_gem_handle_create_tail unlocks dev->object_name_lock. */ ret = drm_gem_handle_create_tail(file_priv, obj, &handle); - drm_gem_object_unreference_unlocked(obj); if (ret) - return ret; + goto err; args->handle = handle; args->size = obj->size; - return 0; +err: + drm_gem_object_unreference_unlocked(obj); + return ret; } /**
|