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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 E277AC3279B for ; Wed, 4 Jul 2018 15:15:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6C38224E6 for ; Wed, 4 Jul 2018 15:15:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A6C38224E6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753216AbeGDPPW (ORCPT ); Wed, 4 Jul 2018 11:15:22 -0400 Received: from mail.netline.ch ([148.251.143.178]:38153 "EHLO netline-mail3.netline.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752533AbeGDPOJ (ORCPT ); Wed, 4 Jul 2018 11:14:09 -0400 Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id 2994F2A6049; Wed, 4 Jul 2018 17:14:07 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id pnXKECfLGF08; Wed, 4 Jul 2018 17:14:06 +0200 (CEST) Received: from kaveri (252.228.127.176.dynamic.wline.res.cust.swisscom.ch [176.127.228.252]) by netline-mail3.netline.ch (Postfix) with ESMTPSA id 8C74C2A6045; Wed, 4 Jul 2018 17:14:06 +0200 (CEST) Received: from daenzer by kaveri with local (Exim 4.91) (envelope-from ) id 1fajTp-0002hn-UC; Wed, 04 Jul 2018 17:14:05 +0200 From: =?UTF-8?q?Michel=20D=C3=A4nzer?= To: =?UTF-8?q?Christian=20K=C3=B6nig?= , Sumit Semwal Cc: linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org Subject: [PATCH v2] dma-buf: Move BUG_ON from _add_shared_fence to _add_shared_inplace Date: Wed, 4 Jul 2018 17:14:05 +0200 Message-Id: <20180704151405.10357-1-michel@daenzer.net> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180626143147.14296-1-michel@daenzer.net> References: <20180626143147.14296-1-michel@daenzer.net> 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: Michel Dänzer Fixes the BUG_ON spuriously triggering under the following circumstances: * reservation_object_reserve_shared is called with shared_count == shared_max - 1, so obj->staged is freed in preparation of an in-place update. * reservation_object_add_shared_fence is called with the first fence, after which shared_count == shared_max. * reservation_object_add_shared_fence is called with a follow-up fence from the same context. In the second reservation_object_add_shared_fence call, the BUG_ON triggers. However, nothing bad would happen in reservation_object_add_shared_inplace, since both fences are from the same context, so they only occupy a single slot. Prevent this by moving the BUG_ON to where an overflow would actually happen (e.g. if a buggy caller didn't call reservation_object_reserve_shared before). v2: * Fix description of breaking scenario (Christian König) * Add bugzilla reference Cc: stable@vger.kernel.org Bugzilla: https://bugs.freedesktop.org/106418 Reviewed-by: Chris Wilson # v1 Reviewed-by: Christian König # v1 Signed-off-by: Michel Dänzer --- drivers/dma-buf/reservation.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 314eb1071cce..532545b9488e 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -141,6 +141,7 @@ reservation_object_add_shared_inplace(struct reservation_object *obj, if (signaled) { RCU_INIT_POINTER(fobj->shared[signaled_idx], fence); } else { + BUG_ON(fobj->shared_count >= fobj->shared_max); RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence); fobj->shared_count++; } @@ -230,10 +231,9 @@ void reservation_object_add_shared_fence(struct reservation_object *obj, old = reservation_object_get_list(obj); obj->staged = NULL; - if (!fobj) { - BUG_ON(old->shared_count >= old->shared_max); + if (!fobj) reservation_object_add_shared_inplace(obj, old, fence); - } else + else reservation_object_add_shared_replace(obj, old, fobj, fence); } EXPORT_SYMBOL(reservation_object_add_shared_fence); -- 2.18.0