From patchwork Tue Feb 18 19:55:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 231152 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=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 41DD2C34049 for ; Tue, 18 Feb 2020 19:58:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B5A324670 for ; Tue, 18 Feb 2020 19:58:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582055930; bh=lUIPdkq7OTx62a3ygJyQLftVTpwgspHMoLu7DyEpkQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=upFgYaTfjbibaekvhVLPZFR9qiz/NR/VpMQQ/xjlNPrLEy4dr1KwPbAQUuRC87YRV vn26Mcp16gRfb9pRECNWDQ2PvI15A/KhwJV3wHEcp69P0UIenwvnB2HYRD0QqTAl6a 6on7drw4YK0Wr70hpguSc6qK0gjqMxQH6vqRAI+U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727906AbgBRT6s (ORCPT ); Tue, 18 Feb 2020 14:58:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:36646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728288AbgBRT6s (ORCPT ); Tue, 18 Feb 2020 14:58:48 -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 EEED420659; Tue, 18 Feb 2020 19:58:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582055927; bh=lUIPdkq7OTx62a3ygJyQLftVTpwgspHMoLu7DyEpkQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wz44PmpY9iMbWkLduWBuJT3Yf+0zDWXPDpvKLgIzIawnp8zw+h1YlwcVc9avLUY5O V5P76uepln9sINVeYtnK0oGUmR+RsxgOLobGjYmeF4EyNd9R3CR4S+wj/FDvU1qvMI 05ACJKVy9l9JxfARDyCk06ILzRUt7JsauAFwlLn4= 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 5.4 34/66] drm/vgem: Close use-after-free race in vgem_gem_create Date: Tue, 18 Feb 2020 20:55:01 +0100 Message-Id: <20200218190431.217621623@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200218190428.035153861@linuxfoundation.org> References: <20200218190428.035153861@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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; }