linux-hardening - [PATCH v2][next] iommu/vt-d: Fix out-bounds-warning in intel_svm_page

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Message-ID: <20210414201403.GA392764@embeddedor>
Date:   Wed, 14 Apr 2021 15:14:03 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2][next] iommu/vt-d: Fix out-bounds-warning in
 intel_svm_page_response()

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@...nel.org>
---
Changes in v2:
 - Fix another instance of this same issue in prq_event_thread().

 drivers/iommu/intel/svm.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
index 5165cea90421..332365ec3195 100644
--- a/drivers/iommu/intel/svm.c
+++ b/drivers/iommu/intel/svm.c
@@ -1020,9 +1020,10 @@ static irqreturn_t prq_event_thread(int irq, void *d)
 			resp.qw2 = 0;
 			resp.qw3 = 0;
 
-			if (req->priv_data_present)
-				memcpy(&resp.qw2, req->priv_data,
-				       sizeof(req->priv_data));
+			if (req->priv_data_present) {
+				resp.qw2 = req->priv_data[0];
+				resp.qw3 = req->priv_data[1];
+			}
 			qi_submit_sync(iommu, &resp, 1, 0);
 		}
 prq_advance:
@@ -1194,9 +1195,10 @@ 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));
+		if (private_present) {
+			desc.qw2 = prm->private_data[0];
+			desc.qw3 = prm->private_data[1];
+		}
 
 		qi_submit_sync(iommu, &desc, 1, 0);
 	}
-- 
2.27.0