From patchwork Wed Sep 16 13:34:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Shevchenko X-Patchwork-Id: 11780837 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3EF9192C for ; Wed, 16 Sep 2020 20:35:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25E422087D for ; Wed, 16 Sep 2020 20:35:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727047AbgIPUeD (ORCPT ); Wed, 16 Sep 2020 16:34:03 -0400 Received: from mga09.intel.com ([134.134.136.24]:6031 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726900AbgIPRMy (ORCPT ); Wed, 16 Sep 2020 13:12:54 -0400 IronPort-SDR: dK4pn6I6l80sleAiyOCJKEm4sxk7rOvb2rIY9cZvyixr/QgWFNtTxkxQb/LpG4dWuYsYhCPAJt 5vLvR6b7RM+w== X-IronPort-AV: E=McAfee;i="6000,8403,9745"; a="160390001" X-IronPort-AV: E=Sophos;i="5.76,432,1592895600"; d="scan'208";a="160390001" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2020 06:34:59 -0700 IronPort-SDR: 3JJFnI70kQiYyeypnqq1TpKKMdJAP8B8LRsBX/ot/I1YGYbnmzLwN/4dUd7OTjAZGD++SLqqxZ 5BiCTPFzOJ7g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,432,1592895600"; d="scan'208";a="331680617" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga004.fm.intel.com with ESMTP; 16 Sep 2020 06:34:57 -0700 Received: by black.fi.intel.com (Postfix, from userid 1003) id A138F277; Wed, 16 Sep 2020 16:34:56 +0300 (EEST) From: Andy Shevchenko To: Dan Williams , dmaengine@vger.kernel.org, Vinod Koul Cc: Andy Shevchenko , Vladimir Murzin Subject: [PATCH v1 2/3] dmaengine: dmatest: Check list for emptiness before access its last entry Date: Wed, 16 Sep 2020 16:34:55 +0300 Message-Id: <20200916133456.79280-2-andriy.shevchenko@linux.intel.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200916133456.79280-1-andriy.shevchenko@linux.intel.com> References: <20200916133456.79280-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Sender: dmaengine-owner@vger.kernel.org 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 --- 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 4c9a9d7b48bb..757eb1727a04 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;