[PATCH 17/23] iommu/vt-d: Fix out-bounds-warning in intel/svm.c

[Lu Baolu <baolu.lu@linux.intel.com>]

From: "Gustavo A. R. Silva" <gustavoars@kernel.org>

Replace a couple of calls to memcpy() with simple assignments in order
to fix the following out-of-bounds warning:

drivers/iommu/intel/svm.c:1198:4: warning: 'memcpy' offset [25, 32] from
    the object at 'desc' is out of the bounds of referenced subobject
    'qw2' with type 'long long unsigned int' at offset 16 [-Warray-bounds]

The problem is that the original code is trying to copy data into a
couple of struct members adjacent to each other in a single call to
memcpy(). This causes a legitimate compiler warning because memcpy()
overruns the length of &desc.qw2 and &resp.qw2, respectively.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210414201403.GA392764@embeddedor
---
 drivers/iommu/intel/svm.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 6bff9a7f9133..9b0f22bc0514 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -870,8 +870,8 @@ static int intel_svm_prq_report(struct intel_iommu *iommu, struct device *dev,
 		 */
 		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_LAST_PAGE;
 		event.fault.prm.flags |= IOMMU_FAULT_PAGE_REQUEST_PRIV_DATA;
-		memcpy(event.fault.prm.private_data, desc->priv_data,
-		       sizeof(desc->priv_data));
+		event.fault.prm.private_data[0] = desc->priv_data[0];
+		event.fault.prm.private_data[1] = desc->priv_data[1];
 	} else if (dmar_latency_enabled(iommu, DMAR_LATENCY_PRQ)) {
 		/*
 		 * If the private data fields are not used by hardware, use it
@@ -910,11 +910,15 @@ static void handle_bad_prq_event(struct intel_iommu *iommu,
 			QI_PGRP_RESP_TYPE;
 	desc.qw1 = QI_PGRP_IDX(req->prg_index) |
 			QI_PGRP_LPIG(req->lpig);
-	desc.qw2 = 0;
-	desc.qw3 = 0;
 
-	if (req->priv_data_present)
-		memcpy(&desc.qw2, req->priv_data, sizeof(req->priv_data));
+	if (req->priv_data_present) {
+		desc.qw2 = req->priv_data[0];
+		desc.qw3 = req->priv_data[1];
+	} else {
+		desc.qw2 = 0;
+		desc.qw3 = 0;
+	}
+
 	qi_submit_sync(iommu, &desc, 1, 0);
 }
 
@@ -1176,12 +1180,14 @@ int intel_svm_page_response(struct device *dev,
 		desc.qw1 = QI_PGRP_IDX(prm->grpid) | QI_PGRP_LPIG(last_page);
 		desc.qw2 = 0;
 		desc.qw3 = 0;
-		if (private_present)
-			memcpy(&desc.qw2, prm->private_data,
-			       sizeof(prm->private_data));
-		else if (prm->private_data[0])
+
+		if (private_present) {
+			desc.qw2 = prm->private_data[0];
+			desc.qw3 = prm->private_data[1];
+		} else if (prm->private_data[0]) {
 			dmar_latency_update(iommu, DMAR_LATENCY_PRQ,
 				ktime_to_ns(ktime_get()) - prm->private_data[0]);
+		}
 
 		qi_submit_sync(iommu, &desc, 1, 0);
 	}
-- 
2.25.1

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