linux-kernel - [PATCH v1] iommu: Avoid use of NULL after WARN_ON

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Message-Id: <20241115190316.28A6B18DFF2@bout3.ijzerbout.nl>
Date: Fri, 15 Nov 2024 19:46:25 +0100
From: Kees Bakker <kees@...erbout.nl>
To: Baolu Lu <baolu.lu@...ux.intel.com>,
    iommu@...ts.linux.dev,
    Tian Kevin <kevin.tian@...el.com>,
    Joerg Roedel <joro@...tes.org>,
    Will Deacon <will@...nel.org>,
    Robin Murphy <robin.murphy@....com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH v1] iommu: Avoid use of NULL after WARN_ON_ONCE

There is a WARN_ON_ONCE to catch an unlikely situation when
domain_remove_dev_pasid can't find the `pasid`. In case it nevertheless
happens we must avoid using a NULL pointer.

Signed-off-by: Kees Bakker <kees@...erbout.nl>
---
 drivers/iommu/intel/iommu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 527f6f89d8a1..204873976ef3 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4096,13 +4096,14 @@ void domain_remove_dev_pasid(struct iommu_domain *domain,
 			break;
 		}
 	}
-	WARN_ON_ONCE(!dev_pasid);
 	spin_unlock_irqrestore(&dmar_domain->lock, flags);
 
 	cache_tag_unassign_domain(dmar_domain, dev, pasid);
 	domain_detach_iommu(dmar_domain, iommu);
-	intel_iommu_debugfs_remove_dev_pasid(dev_pasid);
-	kfree(dev_pasid);
+	if (!WARN_ON_ONCE(!dev_pasid)) {
+		intel_iommu_debugfs_remove_dev_pasid(dev_pasid);
+		kfree(dev_pasid);
+	}
 }
 
 static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid,
-- 
2.47.0