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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 EA09EC4727E for ; Tue, 22 Sep 2020 11:58:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 986F72399A for ; Tue, 22 Sep 2020 11:58:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726541AbgIVL6v (ORCPT ); Tue, 22 Sep 2020 07:58:51 -0400 Received: from mga14.intel.com ([192.55.52.115]:20059 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726531AbgIVL6v (ORCPT ); Tue, 22 Sep 2020 07:58:51 -0400 IronPort-SDR: JT9PJXv5re1V3eJckSRu+JEGHFL5lv1sFeU5+upCqjLfxdUi46TC2NVNjmZ7onZBpXC08StL0q ppTRausYvwtQ== X-IronPort-AV: E=McAfee;i="6000,8403,9751"; a="159875893" X-IronPort-AV: E=Sophos;i="5.77,290,1596524400"; d="scan'208";a="159875893" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Sep 2020 04:58:50 -0700 IronPort-SDR: oaKOA+gkeR7ZpAhstnw7PKP0VdMyT29fgWeqY8p7iXfFxjh30M/tbIE2FBtUDCVK++FppYPAV7 3la+DtsQzf7Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,290,1596524400"; d="scan'208";a="341995095" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga002.fm.intel.com with ESMTP; 22 Sep 2020 04:58:49 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id 30C77161; Tue, 22 Sep 2020 14:58:48 +0300 (EEST) From: Andy Shevchenko To: Dan Williams , dmaengine@vger.kernel.org, Vinod Koul Cc: Andy Shevchenko , Vladimir Murzin , Peter Ujfalusi Subject: [PATCH v2 2/3] dmaengine: dmatest: Check list for emptiness before access its last entry Date: Tue, 22 Sep 2020 14:58:46 +0300 Message-Id: <20200922115847.30100-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200922115847.30100-1-andriy.shevchenko@linux.intel.com> References: <20200922115847.30100-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org After writing a garbage to the channel we get an Oops in dmatest_chan_set() due to access to last entry in the empty list. [ 212.670672] BUG: unable to handle page fault for address: fffffff000000020 [ 212.677562] #PF: supervisor read access in kernel mode [ 212.682702] #PF: error_code(0x0000) - not-present page ... [ 212.710074] RIP: 0010:dmatest_chan_set+0x149/0x2d0 [dmatest] [ 212.715739] Code: e8 cc f9 ff ff 48 8b 1d 0d 55 00 00 48 83 7b 10 00 0f 84 63 01 00 00 48 c7 c7 d0 65 4d c0 e8 ee 4a f5 e1 48 89 c6 48 8b 43 10 <48> 8b 40 20 48 8b 78 58 48 85 ff 0f 84 f5 00 00 00 e8 b1 41 f5 e1 Fix this by checking list for emptiness before accessing its last entry. Fixes: d53513d5dc28 ("dmaengine: dmatest: Add support for multi channel testing") Cc: Vladimir Murzin Signed-off-by: Andy Shevchenko Tested-by: Peter Ujfalusi --- v2: added tag (Peter) drivers/dma/dmatest.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c index ac28d5eea913..f04f32bdf8f7 100644 --- a/drivers/dma/dmatest.c +++ b/drivers/dma/dmatest.c @@ -1267,15 +1267,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp) add_threaded_test(info); /* Check if channel was added successfully */ - dtc = list_last_entry(&info->channels, struct dmatest_chan, node); - - if (dtc->chan) { + if (!list_empty(&info->channels)) { /* * if new channel was not successfully added, revert the * "test_channel" string to the name of the last successfully * added channel. exception for when users issues empty string * to channel parameter. */ + dtc = list_last_entry(&info->channels, struct dmatest_chan, node); if ((strcmp(dma_chan_name(dtc->chan), strim(test_channel)) != 0) && (strcmp("", strim(test_channel)) != 0)) { ret = -EINVAL; -- 2.28.0