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-em... 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; }
/**