linux-kernel - [PATCH v10 1/8] iommu/arm-smmu-v3: Add a missing dma

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b657710166d5ce662f74054a916d81fa8b9545d8.1769476588.git.nicolinc@nvidia.com>
Date: Mon, 26 Jan 2026 19:09:12 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: <will@...nel.org>
CC: <jean-philippe@...aro.org>, <robin.murphy@....com>, <joro@...tes.org>,
	<jgg@...dia.com>, <balbirs@...dia.com>, <miko.lenczewski@....com>,
	<peterz@...radead.org>, <kevin.tian@...el.com>, <praan@...gle.com>,
	<linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH v10 1/8] iommu/arm-smmu-v3: Add a missing dma_wmb() for hitless STE update

When writing a new (previously invalid) valid IOPTE to a page table, then
installing the page table into an STE hitlesslessly (e.g. in S2TTB field),
there is a window before an STE invalidation, where the page-table may be
accessed by SMMU but the new IOPTE is still siting in the CPU cache.

This could occur when we allocate an iommu_domain and immediately install
it hitlessly, while there would be no dma_wmb() for the page table memory
prior to the earliest point of HW reading the STE.

Fix it by adding a dma_wmb() prior to updating the STE.

Fixes: 56e1a4cc2588 ("iommu/arm-smmu-v3: Add unit tests for arm_smmu_write_entry")
Cc: stable@...r.kernel.org
Reported-by: Will Deacon <will@...nel.org>
Closes: https://lore.kernel.org/linux-iommu/aXdlnLLFUBwjT0V5@willie-the-truck/
Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 852379845359..f0e3b407c293 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1236,6 +1236,13 @@ void arm_smmu_write_entry(struct arm_smmu_entry_writer *writer, __le64 *entry,
 	__le64 unused_update[NUM_ENTRY_QWORDS];
 	u8 used_qword_diff;
 
+	/*
+	 * Many of the entry structures have pointers to other structures that
+	 * need to have their updates be visible before any writes of the entry
+	 * happen.
+	 */
+	dma_wmb();
+
 	used_qword_diff =
 		arm_smmu_entry_qword_diff(writer, entry, target, unused_update);
 	if (hweight8(used_qword_diff) == 1) {
-- 
2.43.0