linux-kernel - [PATCH 1/1] iommu: Return right value in iommu_sva_bind

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Message-Id: <20240528042528.71396-1-baolu.lu@linux.intel.com>
Date: Tue, 28 May 2024 12:25:28 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Kevin Tian <kevin.tian@...el.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc: iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 1/1] iommu: Return right value in iommu_sva_bind_device()

iommu_sva_bind_device() should return either a sva bond handle or an
ERR_PTR value in error cases. Existing drivers (idxd and uacce) only
check the return value with IS_ERR(). This could potentially lead to
a kernel NULL pointer dereference issue if the function returns NULL
instead of an error pointer.

In reality, this doesn't cause any problems because iommu_sva_bind_device()
only returns NULL when the kernel is not configured with CONFIG_IOMMU_SVA.
In this case, iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) will
return an error, and the device drivers won't call iommu_sva_bind_device()
at all.

Fixes: 26b25a2b98e4 ("iommu: Bind process address spaces to devices")
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 include/linux/iommu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 7bc8dff7cf6d..17b3f36ad843 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -1533,7 +1533,7 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
 static inline struct iommu_sva *
 iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
 {
-	return NULL;
+	return ERR_PTR(-ENODEV);
 }

 static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
-- 
2.34.1