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,URIBL_BLOCKED,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 8C74AC18E5A for ; Tue, 10 Mar 2020 12:54:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 635772468F for ; Tue, 10 Mar 2020 12:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583844889; bh=uE2tZ0cXXEfqiy3UNn8FOMrI+JRdn0gH0gv8NGuJsVM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HF18VjbHHKN5+oEYSLkFeUJ03zVOIjaiMoOxCCZKy9LjwZG+huKZhAJUXSX6gCFWE lOPWCo+XXUjA9TCb89bcvOVWBo5FYYU3tE+wEA1CIyLFSPDz9nsC5C4g1aol9Soupk iC1xiLI9XPkKLLyYAIGoSckCE0y2SYioCasM3bng= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729118AbgCJMys (ORCPT ); Tue, 10 Mar 2020 08:54:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:33332 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729406AbgCJMyp (ORCPT ); Tue, 10 Mar 2020 08:54:45 -0400 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 A72722468F; Tue, 10 Mar 2020 12:54:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583844885; bh=uE2tZ0cXXEfqiy3UNn8FOMrI+JRdn0gH0gv8NGuJsVM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wt2/7OS+iM9svd2ZY9Q2UMfNtJXyyv+n9fDSNm+JnOF9D2G9ZuPMMfVMR8KkGKL/G sqacA95UWWHIbgp6pd0WeycNzBKh1Tm+DBIOSt/5bUY7MC8itmW9Rtu9PQC2OBEdyv dhl1XtJZN1q9SJ6Ch8sPWR2lUEdlOYu2/RsMkDdc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, John Bates , Chia-I Wu , Gerd Hoffmann Subject: [PATCH 5.4 116/168] drm/virtio: fix resource id creation race Date: Tue, 10 Mar 2020 13:39:22 +0100 Message-Id: <20200310123647.154455955@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200310123635.322799692@linuxfoundation.org> References: <20200310123635.322799692@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: John Bates commit fbb30168c7395b9cfeb9e6f7b0c0bca854a6552d upstream. The previous code was not thread safe and caused undefined behavior from spurious duplicate resource IDs. In this patch, an atomic_t is used instead. We no longer see any duplicate IDs in tests with this change. Fixes: 16065fcdd19d ("drm/virtio: do NOT reuse resource ids") Signed-off-by: John Bates Reviewed-by: Chia-I Wu Link: http://patchwork.freedesktop.org/patch/msgid/20200220225319.45621-1-jbates@chromium.org Signed-off-by: Gerd Hoffmann Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -42,8 +42,8 @@ static int virtio_gpu_resource_id_get(st * "f91a9dd35715 Fix unlinking resources from hash * table." (Feb 2019) fixes the bug. */ - static int handle; - handle++; + static atomic_t seqno = ATOMIC_INIT(0); + int handle = atomic_inc_return(&seqno); *resid = handle + 1; } else { int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);