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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 69899C34026 for ; Tue, 18 Feb 2020 20:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4040F21D56 for ; Tue, 18 Feb 2020 20:04:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582056268; bh=lUIPdkq7OTx62a3ygJyQLftVTpwgspHMoLu7DyEpkQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=GKTfGqM51Q9ltwk7WVnsRbOAzfL6aOE6UhMUYGu2DVt/c9imcxVpRthl1qCeD0p2P AdkEulHwOqvGoIK95bkhP40Oje86N0RpqVQgjW4u+pV25aGvH3Cxuc3frpwGJgnJJg b9MibS4i4lNwErJGr+9rl3NGIWvgrN7ykQ/Ba00w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729151AbgBRUE1 (ORCPT ); Tue, 18 Feb 2020 15:04:27 -0500 Received: from mail.kernel.org ([198.145.29.99]:44804 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728753AbgBRUDb (ORCPT ); Tue, 18 Feb 2020 15:03:31 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2C61221D56; Tue, 18 Feb 2020 20:03:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582056210; bh=lUIPdkq7OTx62a3ygJyQLftVTpwgspHMoLu7DyEpkQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RgA0LqaDN8xShlC0RI1UK7Mfj2WO94r+5j+3pmEmzQJWNTPxOQnR3oyB/fLiF6YZG Z5xgUT7sajxloxNl6rtTqO4TrY2br/lHA0g9sonlekCPma9Uz3yoP3Q0+7Qd7meAS5 HE1dQXTPdvb1XMqWSQR0HMJQ4HhOjq9sk7AfCwE0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Carpenter , Hillf Danton , syzbot+0dc4444774d419e916c8@syzkaller.appspotmail.com, Emil Velikov , Daniel Vetter , Sean Paul , Chris Wilson , Eric Anholt , Sam Ravnborg , Rob Clark , Daniel Vetter Subject: [PATCH 5.5 40/80] drm/vgem: Close use-after-free race in vgem_gem_create Date: Tue, 18 Feb 2020 20:55:01 +0100 Message-Id: <20200218190436.210849575@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200218190432.043414522@linuxfoundation.org> References: <20200218190432.043414522@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Vetter commit 4b848f20eda5974020f043ca14bacf7a7e634fc8 upstream. 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 Reported-by: syzbot+0dc4444774d419e916c8@syzkaller.appspotmail.com 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 Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200202132133.1891846-1-daniel.vetter@ffwll.ch Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/vgem/vgem_drv.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- 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_c 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 d 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; }