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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A2FDCCA481 for ; Thu, 23 Jun 2022 17:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230521AbiFWRNn (ORCPT ); Thu, 23 Jun 2022 13:13:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233260AbiFWRMn (ORCPT ); Thu, 23 Jun 2022 13:12:43 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC9F4FD0F; Thu, 23 Jun 2022 09:58:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9A136B8248C; Thu, 23 Jun 2022 16:58:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C090C341C4; Thu, 23 Jun 2022 16:58:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1656003494; bh=16b6PY1TeUWnE/IpvugwSpZqVE6hi1bxiN09PYoNemo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mq6KZZGW+cJ9z5U8ff7k7pFIACxDKlTFU7NMwM0YJfLDPP3xuVsZ2qDouReogHZqR wZM6SgbcKR9zHYgMplN1IPrmaqvUsk3OFkFBkahtAYwqrfqy6estv8RiWjy6BEEjtr Pa5wWKxQnO5R0kxOJ5jwnXIOgpLpiP/Pc36qbyFI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Halil Pasic , Oleksandr Natalenko , Christoph Hellwig , Linus Torvalds , Ovidiu Panait , Ben Hutchings Subject: [PATCH 4.9 255/264] Reinstate some of "swiotlb: rework "fix info leak with DMA_FROM_DEVICE"" Date: Thu, 23 Jun 2022 18:44:08 +0200 Message-Id: <20220623164351.280903965@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623164344.053938039@linuxfoundation.org> References: <20220623164344.053938039@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: stable@vger.kernel.org From: Linus Torvalds commit 901c7280ca0d5e2b4a8929fbe0bfb007ac2a6544 upstream. Halil Pasic points out [1] that the full revert of that commit (revert in bddac7c1e02b), and that a partial revert that only reverts the problematic case, but still keeps some of the cleanups is probably better.  And that partial revert [2] had already been verified by Oleksandr Natalenko to also fix the issue, I had just missed that in the long discussion. So let's reinstate the cleanups from commit aa6f8dcbab47 ("swiotlb: rework "fix info leak with DMA_FROM_DEVICE""), and effectively only revert the part that caused problems. Link: https://lore.kernel.org/all/20220328013731.017ae3e3.pasic@linux.ibm.com/ [1] Link: https://lore.kernel.org/all/20220324055732.GB12078@lst.de/ [2] Link: https://lore.kernel.org/all/4386660.LvFx2qVVIh@natalenko.name/ [3] Suggested-by: Halil Pasic Tested-by: Oleksandr Natalenko Cc: Christoph Hellwig Signed-off-by: Linus Torvalds [OP: backport to 4.14: apply swiotlb_tbl_map_single() changes in lib/swiotlb.c] Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- Documentation/DMA-attributes.txt | 10 ---------- include/linux/dma-mapping.h | 7 ------- lib/swiotlb.c | 12 ++++++++---- 3 files changed, 8 insertions(+), 21 deletions(-) --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -143,13 +143,3 @@ So, this provides a way for drivers to a where allocation failures are not a problem, and shouldn't bother the logs. NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC. - -DMA_ATTR_PRIVILEGED -------------------- - -Some advanced peripherals such as remote processors and GPUs perform -accesses to DMA buffers in both privileged "supervisor" and unprivileged -"user" modes. This attribute is used to indicate to the DMA-mapping -subsystem that the buffer is fully accessible at the elevated privilege -level (and ideally inaccessible or at least read-only at the -lesser-privileged levels). --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -61,13 +61,6 @@ * allocation failure reports (similarly to __GFP_NOWARN). */ #define DMA_ATTR_NO_WARN (1UL << 8) -/* - * This is a hint to the DMA-mapping subsystem that the device is expected - * to overwrite the entire mapped size, thus the caller does not require any - * of the previous buffer contents to be preserved. This allows - * bounce-buffering implementations to optimise DMA_FROM_DEVICE transfers. - */ -#define DMA_ATTR_OVERWRITE (1UL << 10) /* * A dma_addr_t can hold any valid DMA or bus address for the platform. --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -532,10 +532,14 @@ found: */ for (i = 0; i < nslots; i++) io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT); - if (!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE || - dir == DMA_BIDIRECTIONAL) - swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE); - + /* + * When dir == DMA_FROM_DEVICE we could omit the copy from the orig + * to the tlb buffer, if we knew for sure the device will + * overwirte the entire current content. But we don't. Thus + * unconditional bounce may prevent leaking swiotlb content (i.e. + * kernel memory) to user-space. + */ + swiotlb_bounce(orig_addr, tlb_addr, size, DMA_TO_DEVICE); return tlb_addr; } EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);