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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10D1DC433EF for ; Mon, 25 Oct 2021 19:47:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F171E611AD for ; Mon, 25 Oct 2021 19:47:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237179AbhJYTt6 (ORCPT ); Mon, 25 Oct 2021 15:49:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:59364 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237420AbhJYTnh (ORCPT ); Mon, 25 Oct 2021 15:43:37 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7285A6115C; Mon, 25 Oct 2021 19:37:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1635190674; bh=u/qQM1UwUGSCz6+revutruyyLKl9Cqwd2FYne25gnKs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NSkzYuA2BtQ6igOlWmyXX7SuOIhJCK1ibg/LVhtG4b3Lw9M8/eN6W1OiY+sY28wbS pb5b+WZ4rJkDpexVRFJFV9Q4Fq5R1G4z7qU5iLheOBu1yrlYhVo/2eNyYbvPoxuOPm N3SRO4tc5xb2TUi7r7Q8NNK0NcEL8mHuOQcTT4VA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Gerald Schaefer , Christoph Hellwig , Sasha Levin Subject: [PATCH 5.14 026/169] dma-debug: fix sg checks in debug_dma_map_sg() Date: Mon, 25 Oct 2021 21:13:27 +0200 Message-Id: <20211025191021.146334747@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211025191017.756020307@linuxfoundation.org> References: <20211025191017.756020307@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Gerald Schaefer [ Upstream commit 293d92cbbd2418ca2ba43fed07f1b92e884d1c77 ] 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 broken logic in debug_dma_map_sg(). check_for_illegal_area() checks 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() will contain 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 physical start address of an sg element, and add the DMA length for the overlap check, which could result in the false warning, because the DMA length can be larger than the actual single sg element length. 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"). While at it, as suggested by Robin Murphy, also move check_for_stack() inside the new loop, as it is similarly concerned with validating the individual sg elements. Link: https://lore.kernel.org/lkml/20210705185252.4074653-1-gerald.schaefer@linux.ibm.com Fixes: 884d05970bfb ("dma-debug: use sg_dma_len accessor") Signed-off-by: Gerald Schaefer Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- kernel/dma/debug.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c index 70519f67556f..fad3c77c1da1 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) { + check_for_stack(dev, sg_page(s), s->offset); + 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) @@ -1314,12 +1320,6 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg, entry->sg_call_ents = nents; entry->sg_mapped_ents = mapped_ents; - 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); -- 2.33.0