linux-kernel - [PATCH] dmaengine: idxd: Only call idxd_enable_system_pasid if succeeded in enabling SVA feature

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Message-Id: <20220625221333.214589-1-jsnitsel@redhat.com>
Date:   Sat, 25 Jun 2022 15:13:33 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     dmaengine@...r.kernel.org
Cc:     Vinod Koul <vkoul@...nel.org>, linux-kernel@...r.kernel.org,
        Dave Jiang <dave.jiang@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH] dmaengine: idxd: Only call idxd_enable_system_pasid if succeeded in enabling SVA feature

iommu_sva_bind_device requires that iommu_dev_enable_feature has been
previously called with IOMMU_DEV_FEAT_SVA, and succeeded. Without this
it is possible to run into a situation where you will dereference a
null pointer if the intel_iommu driver is not enabled.

Note: checkpatch didn't like the suggested addition of braces for the
      first arm of the "if (idxd_enable_system_pasid)" block.

Fixes: 42a1b73852c4 ("dmaengine: idxd: Separate user and kernel pasid enabling")
Cc: Vinod Koul <vkoul@...nel.org>
Cc: linux-kernel@...r.kernel.org
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
---
 drivers/dma/idxd/init.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 355fb3ef4cbf..5b49fd5c1e25 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -514,13 +514,14 @@ static int idxd_probe(struct idxd_device *idxd)
 	if (IS_ENABLED(CONFIG_INTEL_IDXD_SVM) && sva) {
 		if (iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA))
 			dev_warn(dev, "Unable to turn on user SVA feature.\n");
-		else
+		else {
 			set_bit(IDXD_FLAG_USER_PASID_ENABLED, &idxd->flags);
 
-		if (idxd_enable_system_pasid(idxd))
-			dev_warn(dev, "No in-kernel DMA with PASID.\n");
-		else
-			set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags);
+			if (idxd_enable_system_pasid(idxd))
+				dev_warn(dev, "No in-kernel DMA with PASID.\n");
+			else
+				set_bit(IDXD_FLAG_PASID_ENABLED, &idxd->flags);
+		}
 	} else if (!sva) {
 		dev_warn(dev, "User forced SVA off via module param.\n");
 	}
-- 
2.36.1