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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 69790C07E99 for ; Mon, 5 Jul 2021 18:53:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 492506197B for ; Mon, 5 Jul 2021 18:53:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229990AbhGESzu (ORCPT ); Mon, 5 Jul 2021 14:55:50 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:53476 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229970AbhGESzt (ORCPT ); Mon, 5 Jul 2021 14:55:49 -0400 Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 165IZAxO082841; Mon, 5 Jul 2021 14:53:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=pp1; bh=tBLhHqmv8Xr1QxendNUR/DvIJZUmas2B18j2RZcJe90=; b=VNCxy8+JCw6kjy+bxizvOMve0X8Ha6lplJrGJoRB8hxmSpv2nm4NFRKPgSKvflnxggpN RMxvgIc46dgqUVTO2iu57KSrvx6xxJTi/7Pwat0FrGPIlogo+YA1rwnW01aK3eVowqO9 XZ18Cvm6iN58JbDDB/ynkCTHvMO4svQirFDlhNf3AL1dKCE6TPs3XQ7tb8/O1fklsSDI iQsXlALN/hTLpKJqifZcatRzYGVMAv2pUNMc1bI40JrVp4OC8iddckmx2r+wWZno6ZD4 JtnzHPReXrFtBG60HyJyRe3lwaYqUUzDPTrvvdyh/YMZNnEvjbE/j/j0UeQd94EI3P8l uA== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com with ESMTP id 39m6k01j6d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 05 Jul 2021 14:53:03 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 165IoBnc015081; Mon, 5 Jul 2021 18:53:01 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma06ams.nl.ibm.com with ESMTP id 39jf5h8ww8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 05 Jul 2021 18:53:01 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 165Iqwge33423678 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 5 Jul 2021 18:52:58 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 42ED742042; Mon, 5 Jul 2021 18:52:58 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 02EEB4203F; Mon, 5 Jul 2021 18:52:58 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 5 Jul 2021 18:52:57 +0000 (GMT) From: Gerald Schaefer To: Christoph Hellwig , Cc: LKML , linux-s390 , Niklas Schnelle Subject: [RFC PATCH 1/1] dma-debug: fix check_for_illegal_area() in debug_dma_map_sg() Date: Mon, 5 Jul 2021 20:52:52 +0200 Message-Id: <20210705185252.4074653-2-gerald.schaefer@linux.ibm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210705185252.4074653-1-gerald.schaefer@linux.ibm.com> References: <20210705185252.4074653-1-gerald.schaefer@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: gV9b_hflviYi124sNTpneb2U3SZKbgLQ X-Proofpoint-ORIG-GUID: gV9b_hflviYi124sNTpneb2U3SZKbgLQ X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-05_10:2021-07-02,2021-07-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxscore=0 spamscore=0 impostorscore=0 mlxlogscore=999 clxscore=1015 malwarescore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107050099 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following warning occurred sporadically on s390: DMA-API: nvme 0006:00:00.0: device driver maps memory from kernel text or rodata [addr=0000000048cc5e2f] [len=131072] WARNING: CPU: 4 PID: 825 at kernel/dma/debug.c:1083 check_for_illegal_area+0xa8/0x138 It is a false-positive warning, due to a broken logic in debug_dma_map_sg(). check_for_illegal_area() should check for overlay of sg elements with kernel text or rodata. It is called with sg_dma_len(s) instead of s->length as parameter. After the call to ->map_sg(), sg_dma_len() contains the length of possibly combined sg elements in the DMA address space, and not the individual sg element length, which would be s->length. The check will then use the kernel start address of an sg element, and add the DMA length for overlap check, which can result in the false-positive warning because the DMA length can be larger than the actual single sg element length in kernel address space. In addition, the call to check_for_illegal_area() happens in the iteration over mapped_ents, which will not include all individual sg elements if any of them were combined in ->map_sg(). Fix this by using s->length instead of sg_dma_len(s). Also put the call to check_for_illegal_area() in a separate loop, iterating over all the individual sg elements ("nents" instead of "mapped_ents"). Fixes: 884d05970bfb ("dma-debug: use sg_dma_len accessor") Tested-by: Niklas Schnelle Signed-off-by: Gerald Schaefer --- kernel/dma/debug.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index 14de1271463f..d7d44b7fe7e2 100644 --- a/kernel/dma/debug.c +++ b/kernel/dma/debug.c @@ -1299,6 +1299,12 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg, if (unlikely(dma_debug_disabled())) return; + for_each_sg(sg, s, nents, i) { + if (!PageHighMem(sg_page(s))) { + check_for_illegal_area(dev, sg_virt(s), s->length); + } + } + for_each_sg(sg, s, mapped_ents, i) { entry = dma_entry_alloc(); if (!entry) @@ -1316,10 +1322,6 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg, check_for_stack(dev, sg_page(s), s->offset); - if (!PageHighMem(sg_page(s))) { - check_for_illegal_area(dev, sg_virt(s), sg_dma_len(s)); - } - check_sg_segment(dev, s); add_dma_entry(entry); -- 2.25.1