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From:   Lu Baolu <baolu.lu@linux.intel.com>
To:     David Woodhouse <dwmw2@infradead.org>,
        Joerg Roedel <joro@8bytes.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Christoph Hellwig <hch@lst.de>
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        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
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        Lu Baolu <baolu.lu@linux.intel.com>
Subject: [PATCH v4 3/9] swiotlb: Zero out bounce buffer for untrusted device
Date:   Mon,  3 Jun 2019 09:16:14 +0800
Message-Id: <20190603011620.31999-4-baolu.lu@linux.intel.com>
In-Reply-To: <20190603011620.31999-1-baolu.lu@linux.intel.com>
References: <20190603011620.31999-1-baolu.lu@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This is necessary to avoid exposing valid kernel data to any
milicious device.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 kernel/dma/swiotlb.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index f956f785645a..ed41eb7f6131 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -35,6 +35,7 @@
 #include <linux/scatterlist.h>
 #include <linux/mem_encrypt.h>
 #include <linux/set_memory.h>
+#include <linux/pci.h>
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 #endif
@@ -560,6 +561,11 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 	 */
 	for (i = 0; i < nslots; i++)
 		io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
+
+	/* Zero out the bounce buffer if the consumer is untrusted. */
+	if (dev_is_untrusted(hwdev))
+		memset(phys_to_virt(tlb_addr), 0, alloc_size);
+
 	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
 	    (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
 		swiotlb_bounce(orig_addr, tlb_addr, mapping_size, DMA_TO_DEVICE);
-- 
2.17.1