From: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> commit 0ea2ea42b31abc1141f2fd3911f952a97d401fcb upstream. We need to keep the reference to the drm_gem_object until the last access by vkms_dumb_create. Therefore, the put the object after it is used. This fixes a use-after-free issue reported by syzbot. While here, change vkms_gem_create() symbol to static. Reported-and-tested-by: syzbot+e3372a2afe1e7ef04bc7@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx> Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20200427214405.13069-1-ezequiel@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/vkms/vkms_drv.h | 5 ----- drivers/gpu/drm/vkms/vkms_gem.c | 11 ++++++----- 2 files changed, 6 insertions(+), 10 deletions(-) --- a/drivers/gpu/drm/vkms/vkms_drv.h +++ b/drivers/gpu/drm/vkms/vkms_drv.h @@ -62,11 +62,6 @@ int vkms_output_init(struct vkms_device struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev); /* Gem stuff */ -struct drm_gem_object *vkms_gem_create(struct drm_device *dev, - struct drm_file *file, - u32 *handle, - u64 size); - int vkms_gem_fault(struct vm_fault *vmf); int vkms_dumb_create(struct drm_file *file, struct drm_device *dev, --- a/drivers/gpu/drm/vkms/vkms_gem.c +++ b/drivers/gpu/drm/vkms/vkms_gem.c @@ -93,10 +93,10 @@ int vkms_gem_fault(struct vm_fault *vmf) return ret; } -struct drm_gem_object *vkms_gem_create(struct drm_device *dev, - struct drm_file *file, - u32 *handle, - u64 size) +static struct drm_gem_object *vkms_gem_create(struct drm_device *dev, + struct drm_file *file, + u32 *handle, + u64 size) { struct vkms_gem_object *obj; int ret; @@ -109,7 +109,6 @@ struct drm_gem_object *vkms_gem_create(s return ERR_CAST(obj); ret = drm_gem_handle_create(file, &obj->gem, handle); - drm_gem_object_put_unlocked(&obj->gem); if (ret) return ERR_PTR(ret); @@ -138,6 +137,8 @@ int vkms_dumb_create(struct drm_file *fi args->size = gem_obj->size; args->pitch = pitch; + drm_gem_object_put_unlocked(gem_obj); + DRM_DEBUG_DRIVER("Created object of size %lld\n", size); return 0;
