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 A6A24C433F5 for ; Tue, 1 Mar 2022 20:14:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229603AbiCAUOq (ORCPT ); Tue, 1 Mar 2022 15:14:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237665AbiCAUOp (ORCPT ); Tue, 1 Mar 2022 15:14:45 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 837B43C4A6; Tue, 1 Mar 2022 12:14:03 -0800 (PST) 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 DAD36B81CB6; Tue, 1 Mar 2022 20:14:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B9D5C340F2; Tue, 1 Mar 2022 20:13:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646165640; bh=p41vAUTEwrbRH9Ku4EH0h2EV1Rk8kpZdtERxY0TL2yg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NKjSSlJTHTDuL4u2v3GWRa+ZqEHAMbCfzXHiftI7XvFzS1HXGI75+UCfo1FWERTPV IbJZR4QMdL/KS/1P7HuFUJoZkhmUeaytDyKcKgrKiT10+MEcwv/GCt/DpvHQy3FuKP X/lBfDSlDIeOVrEm7PH+2ATYsx1F5uE2XgiZAh3GxiLkbEJ5p4+uWwms0Uaiv62+sz dB5V/7QW1Dap3HVllRxaeHWkDEYOW4kQuZjFuXWzY3wtxMEQ3mATYcmT7mOR/GQsCt c30ZfA2rFGuJzubdKSbGZQHubQi51vviJFUlD9GzjGlY1QcHc0+MnaIUPeCK27TkSS QB+fGZl/4Dzmw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Halil Pasic , Christoph Hellwig , Sasha Levin , corbet@lwn.net, m.szyprowski@samsung.com, linux-doc@vger.kernel.org, iommu@lists.linux-foundation.org Subject: [PATCH AUTOSEL 5.16 02/28] swiotlb: fix info leak with DMA_FROM_DEVICE Date: Tue, 1 Mar 2022 15:13:07 -0500 Message-Id: <20220301201344.18191-2-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301201344.18191-1-sashal@kernel.org> References: <20220301201344.18191-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org From: Halil Pasic [ Upstream commit ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e ] The problem I'm addressing was discovered by the LTP test covering cve-2018-1000204. A short description of what happens follows: 1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device. 2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO. 3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV). 4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer. 5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails. One can argue that this is an swiotlb problem, because without swiotlb we leak all zeros, and the swiotlb should be transparent in a sense that it does not affect the outcome (if all other participants are well behaved). Copying the content of the original buffer into the swiotlb buffer is the only way I can think of to make swiotlb transparent in such scenarios. So let's do just that if in doubt, but allow the driver to tell us that the whole mapped buffer is going to be overwritten, in which case we can preserve the old behavior and avoid the performance impact of the extra bounce. Signed-off-by: Halil Pasic Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- Documentation/core-api/dma-attributes.rst | 8 ++++++++ include/linux/dma-mapping.h | 8 ++++++++ kernel/dma/swiotlb.c | 3 ++- 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 1887d92e8e926..17706dc91ec9f 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -130,3 +130,11 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged 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). + +DMA_ATTR_OVERWRITE +------------------ + +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. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index dca2b1355bb13..6150d11a607e1 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -61,6 +61,14 @@ */ #define DMA_ATTR_PRIVILEGED (1UL << 9) +/* + * 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. It can * be given to a device to use as a DMA source or target. It is specific to a diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 8e840fbbed7c7..d958b1201092c 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -582,7 +582,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, mem->slots[index + i].orig_addr = slot_addr(orig_addr, i); tlb_addr = slot_addr(mem->start, index) + offset; if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && - (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) + (!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE || + dir == DMA_BIDIRECTIONAL)) swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE); return tlb_addr; } -- 2.34.1 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 smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3C676C433FE for ; Tue, 1 Mar 2022 20:14:08 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id B793060DCB; Tue, 1 Mar 2022 20:14:07 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ju6KiLMXeuhg; Tue, 1 Mar 2022 20:14:06 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTPS id 3344360A79; Tue, 1 Mar 2022 20:14:06 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0FD9BC0082; Tue, 1 Mar 2022 20:14:06 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id EC1A7C000B for ; Tue, 1 Mar 2022 20:14:04 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id E1FB5409A0 for ; Tue, 1 Mar 2022 20:14:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp4.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=kernel.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id aGbc2nlzW88N for ; Tue, 1 Mar 2022 20:14:04 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by smtp4.osuosl.org (Postfix) with ESMTPS id 131664098E for ; Tue, 1 Mar 2022 20:14:03 +0000 (UTC) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 9CE7E6153D; Tue, 1 Mar 2022 20:14:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B9D5C340F2; Tue, 1 Mar 2022 20:13:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646165640; bh=p41vAUTEwrbRH9Ku4EH0h2EV1Rk8kpZdtERxY0TL2yg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NKjSSlJTHTDuL4u2v3GWRa+ZqEHAMbCfzXHiftI7XvFzS1HXGI75+UCfo1FWERTPV IbJZR4QMdL/KS/1P7HuFUJoZkhmUeaytDyKcKgrKiT10+MEcwv/GCt/DpvHQy3FuKP X/lBfDSlDIeOVrEm7PH+2ATYsx1F5uE2XgiZAh3GxiLkbEJ5p4+uWwms0Uaiv62+sz dB5V/7QW1Dap3HVllRxaeHWkDEYOW4kQuZjFuXWzY3wtxMEQ3mATYcmT7mOR/GQsCt c30ZfA2rFGuJzubdKSbGZQHubQi51vviJFUlD9GzjGlY1QcHc0+MnaIUPeCK27TkSS QB+fGZl/4Dzmw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 5.16 02/28] swiotlb: fix info leak with DMA_FROM_DEVICE Date: Tue, 1 Mar 2022 15:13:07 -0500 Message-Id: <20220301201344.18191-2-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220301201344.18191-1-sashal@kernel.org> References: <20220301201344.18191-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Cc: Sasha Levin , linux-doc@vger.kernel.org, corbet@lwn.net, Halil Pasic , iommu@lists.linux-foundation.org, Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" From: Halil Pasic [ Upstream commit ddbd89deb7d32b1fbb879f48d68fda1a8ac58e8e ] The problem I'm addressing was discovered by the LTP test covering cve-2018-1000204. A short description of what happens follows: 1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV and a corresponding dxferp. The peculiar thing about this is that TUR is not reading from the device. 2) In sg_start_req() the invocation of blk_rq_map_user() effectively bounces the user-space buffer. As if the device was to transfer into it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()") we make sure this first bounce buffer is allocated with GFP_ZERO. 3) For the rest of the story we keep ignoring that we have a TUR, so the device won't touch the buffer we prepare as if the we had a DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device and the buffer allocated by SG is mapped by the function virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here scatter-gather and not scsi generics). This mapping involves bouncing via the swiotlb (we need swiotlb to do virtio in protected guest like s390 Secure Execution, or AMD SEV). 4) When the SCSI TUR is done, we first copy back the content of the second (that is swiotlb) bounce buffer (which most likely contains some previous IO data), to the first bounce buffer, which contains all zeros. Then we copy back the content of the first bounce buffer to the user-space buffer. 5) The test case detects that the buffer, which it zero-initialized, ain't all zeros and fails. One can argue that this is an swiotlb problem, because without swiotlb we leak all zeros, and the swiotlb should be transparent in a sense that it does not affect the outcome (if all other participants are well behaved). Copying the content of the original buffer into the swiotlb buffer is the only way I can think of to make swiotlb transparent in such scenarios. So let's do just that if in doubt, but allow the driver to tell us that the whole mapped buffer is going to be overwritten, in which case we can preserve the old behavior and avoid the performance impact of the extra bounce. Signed-off-by: Halil Pasic Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- Documentation/core-api/dma-attributes.rst | 8 ++++++++ include/linux/dma-mapping.h | 8 ++++++++ kernel/dma/swiotlb.c | 3 ++- 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 1887d92e8e926..17706dc91ec9f 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -130,3 +130,11 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged 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). + +DMA_ATTR_OVERWRITE +------------------ + +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. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index dca2b1355bb13..6150d11a607e1 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -61,6 +61,14 @@ */ #define DMA_ATTR_PRIVILEGED (1UL << 9) +/* + * 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. It can * be given to a device to use as a DMA source or target. It is specific to a diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 8e840fbbed7c7..d958b1201092c 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -582,7 +582,8 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, mem->slots[index + i].orig_addr = slot_addr(orig_addr, i); tlb_addr = slot_addr(mem->start, index) + offset; if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && - (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) + (!(attrs & DMA_ATTR_OVERWRITE) || dir == DMA_TO_DEVICE || + dir == DMA_BIDIRECTIONAL)) swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE); return tlb_addr; } -- 2.34.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu