Hi Steve and others. On Fri, Jul 10, 2020 at 06:40:26PM -0400, Steve Cohen wrote: > BUG: KASAN: use-after-free in drm_gem_open_ioctl > > There is potential for use-after-free here if the GEM object > handle is closed between the idr lookup and retrieving the size > from the object since a local reference is not being held at that > point. Hold the local reference while the object can still be > accessed to resolve this. > > Signed-off-by: Steve Cohen <cohens@xxxxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_gem.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 7bf628e..4b2891c 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -898,14 +898,15 @@ 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 out; > > args->handle = handle; > args->size = obj->size; > > - return 0; > +out: > + drm_gem_object_put_unlocked(obj); > + return ret; Lookign at drm_gem_flink_ioctl() that is implmented just above this functions there are two things that I noted. 1) In drm_gem_flink_ioctl() the label is named "err:" - and my OCD likes that similar labels have the same name. 2) The function takes the object_name_lock but fails to release it in the error situation. Danile Vetter updated the locking in 20228c447846da9399ead53fdbbc8ab69b47788a ("drm/gem: completely close gem_open vs. gem_close races") but I failed to follow it all. Sam > } > > /** > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel