From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F2DCC35249 for ; Sun, 2 Feb 2020 15:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1693720679 for ; Sun, 2 Feb 2020 15:39:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726881AbgBBPjY (ORCPT ); Sun, 2 Feb 2020 10:39:24 -0500 Received: from asavdk3.altibox.net ([109.247.116.14]:46640 "EHLO asavdk3.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726880AbgBBPjY (ORCPT ); Sun, 2 Feb 2020 10:39:24 -0500 Received: from ravnborg.org (unknown [158.248.194.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by asavdk3.altibox.net (Postfix) with ESMTPS id BAA2520029; Sun, 2 Feb 2020 16:39:17 +0100 (CET) Date: Sun, 2 Feb 2020 16:39:16 +0100 From: Sam Ravnborg To: Daniel Vetter Cc: DRI Development , Rob Clark , Hillf Danton , Intel Graphics Development , stable@vger.kernel.org, Sean Paul , Daniel Vetter , Dan Carpenter , Emil Velikov Subject: Re: [PATCH] drm/vgem: Close use-after-free race in vgem_gem_create Message-ID: <20200202153915.GA8034@ravnborg.org> References: <20200202132133.1891846-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200202132133.1891846-1-daniel.vetter@ffwll.ch> User-Agent: Mutt/1.10.1 (2018-07-13) X-CMAE-Score: 0 X-CMAE-Analysis: v=2.3 cv=eMA9ckh1 c=1 sm=1 tr=0 a=UWs3HLbX/2nnQ3s7vZ42gw==:117 a=UWs3HLbX/2nnQ3s7vZ42gw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=yPCof4ZbAAAA:8 a=QY18SFpNAAAA:8 a=hSkVLCK3AAAA:8 a=VwQbUJbxAAAA:8 a=QX4gbG5DAAAA:8 a=cm27Pg_UAAAA:8 a=taGs_qngAAAA:8 a=-VAfIpHNAAAA:8 a=7gkXJVJtAAAA:8 a=QyXUC8HyAAAA:8 a=e5mUnYsNAAAA:8 a=PZMVLxdsxIagqOrAZEMA:9 a=CjuIK1q_8ugA:10 a=LYL6_n6_bXSRrjLcjcND:22 a=cQPPKAXgyycSBL8etih5:22 a=AjGcO6oz07-iQ99wixmX:22 a=AbAUZ8qAyYyZVLSsDulk:22 a=xmb-EsYY8bH0VWELuYED:22 a=DM_PlaNYpjARcMQr2apF:22 a=srlwD-8ojaedGGhPAyx8:22 a=E9Po1WZjFZOl8hwRPBS3:22 a=Vxmtnl_E_bksehYqCbjh:22 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Hi Daniel. On Sun, Feb 02, 2020 at 02:21:33PM +0100, Daniel Vetter wrote: > There's two references floating around here (for the object reference, > not the handle_count reference, that's a different thing): > > - The temporary reference held by vgem_gem_create, acquired by > creating the object and released by calling > drm_gem_object_put_unlocked. > > - The reference held by the object handle, created by > drm_gem_handle_create. This one generally outlives the function, > except if a 2nd thread races with a GEM_CLOSE ioctl call. > > So usually everything is correct, except in that race case, where the > access to gem_object->size could be looking at freed data already. > Which again isn't a real problem (userspace shot its feet off already > with the race, we could return garbage), but maybe someone can exploit > this as an information leak. > > Cc: Dan Carpenter > Cc: Hillf Danton > Cc: Reported-by: syzbot+0dc4444774d419e916c8@syzkaller.appspotmail.com ^^ Small typo > Cc: stable@vger.kernel.org > Cc: Emil Velikov > Cc: Daniel Vetter > Cc: Sean Paul > Cc: Chris Wilson > Cc: Eric Anholt > Cc: Sam Ravnborg > Cc: Rob Clark > Signed-off-by: Daniel Vetter > --- > drivers/gpu/drm/vgem/vgem_drv.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c > index 5bd60ded3d81..909eba43664a 100644 > --- a/drivers/gpu/drm/vgem/vgem_drv.c > +++ b/drivers/gpu/drm/vgem/vgem_drv.c > @@ -196,9 +196,10 @@ static struct drm_gem_object *vgem_gem_create(struct drm_device *dev, > return ERR_CAST(obj); > > ret = drm_gem_handle_create(file, &obj->base, handle); > - drm_gem_object_put_unlocked(&obj->base); > - if (ret) > + if (ret) { > + drm_gem_object_put_unlocked(&obj->base); > return ERR_PTR(ret); > + } > > return &obj->base; > } > @@ -221,7 +222,9 @@ static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device *dev, > args->size = gem_object->size; > args->pitch = pitch; > > - DRM_DEBUG("Created object of size %lld\n", size); > + drm_gem_object_put_unlocked(gem_object); > + > + DRM_DEBUG("Created object of size %llu\n", args->size); > > return 0; > } > -- > 2.24.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel