linux-kernel - [PATCH v2 1/5] iommu/vt-d: Sanitize set bits in pasid_set

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Message-ID: <20251227175728.4358-2-dmaluka@chromium.org>
Date: Sat, 27 Dec 2025 18:57:24 +0100
From: Dmytro Maluka <dmaluka@...omium.org>
To: David Woodhouse <dwmw2@...radead.org>,
	Lu Baolu <baolu.lu@...ux.intel.com>,
	iommu@...ts.linux.dev
Cc: Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	linux-kernel@...r.kernel.org,
	"Vineeth Pillai (Google)" <vineeth@...byteword.org>,
	Aashish Sharma <aashish@...hishsharma.net>,
	Grzegorz Jaszczyk <jaszczyk@...omium.org>,
	Chuanxiao Dong <chuanxiao.dong@...el.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Dmytro Maluka <dmaluka@...omium.org>
Subject: [PATCH v2 1/5] iommu/vt-d: Sanitize set bits in pasid_set_bits()

When setting PASID entry bits via pasid_set_*() helpers, apply the
specified mask to the specified bits to be set, as a safety measure
in case the caller accidentally passes a value that exceeds the
specified mask. Also warn if that happens.

Suggested-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Dmytro Maluka <dmaluka@...omium.org>
---
 drivers/iommu/intel/pasid.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/pasid.h b/drivers/iommu/intel/pasid.h
index b4c85242dc79..39acd3efa3ab 100644
--- a/drivers/iommu/intel/pasid.h
+++ b/drivers/iommu/intel/pasid.h
@@ -113,8 +113,10 @@ static inline void pasid_set_bits(u64 *ptr, u64 mask, u64 bits)
 {
 	u64 old;
 
+	WARN_ON_ONCE(bits & ~mask);
+
 	old = READ_ONCE(*ptr);
-	WRITE_ONCE(*ptr, (old & ~mask) | bits);
+	WRITE_ONCE(*ptr, (old & ~mask) | (bits & mask));
 }
 
 static inline u64 pasid_get_bits(u64 *ptr)
-- 
2.47.3