On Mon, Jul 20, 2020 at 06:30:50PM -0400, Steve Cohen wrote: > 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@xxxxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_gem.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 7bf628e..ee2058a 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -871,9 +871,6 @@ drm_gem_flink_ioctl(struct drm_device *dev, void *data, > * @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; > } > > /** As this seems to fix an important issue, any reason it wasn't cc: stable on it so that it gets backported properly? How about a "Fixes:" tag so that we know what commit id it fixes so we know how far back to backport things? And a hint to the maintainers that "this is an issue that needs to get into 5.8-final, it shouldn't wait around longer please" would have also been nice to see :) And what chagned from v1, aren't you supposed to list that somewhere in the changelog or below the --- line (never remember what DRM drivers want here...) Care to send a v3? thanks, greg k-h
