linux-kernel - [PATCH v2 2/8] iommu: Validate that devices match domains

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Message-Id: <0f78ba36a7b31a0d534416e56ea0f1af0efc2659.1674753627.git.robin.murphy@arm.com>
Date:   Thu, 26 Jan 2023 18:26:17 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     joro@...tes.org, will@...nel.org
Cc:     iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, hch@....de,
        jgg@...dia.com, baolu.lu@...ux.intel.com
Subject: [PATCH v2 2/8] iommu: Validate that devices match domains

Before we can allow drivers to coexist, we need to make sure that one
driver's domain ops can't misinterpret another driver's dev_iommu_priv
data. To that end, add a token to the domain so we can remember how it
was allocated - for now this may as well be the device ops, since they
still correlate 1:1 with drivers. We can trust ourselves for internal
default domain attachment, so add the check where it covers both the
external attach interfaces.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---

v2: Tweaked commit message

 drivers/iommu/iommu.c | 13 +++++++++----
 include/linux/iommu.h |  1 +
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b27f5d3453bb..d48e5499e0fa 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1941,20 +1941,22 @@ EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
 static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
 						 unsigned type)
 {
+	const struct iommu_ops *ops = bus ? bus->iommu_ops : NULL;
 	struct iommu_domain *domain;
 
-	if (bus == NULL || bus->iommu_ops == NULL)
+	if (!ops)
 		return NULL;
 
-	domain = bus->iommu_ops->domain_alloc(type);
+	domain = ops->domain_alloc(type);
 	if (!domain)
 		return NULL;
 
 	domain->type = type;
+	domain->owner = ops;
 	/* Assume all sizes by default; the driver may override this later */
-	domain->pgsize_bitmap = bus->iommu_ops->pgsize_bitmap;
+	domain->pgsize_bitmap = ops->pgsize_bitmap;
 	if (!domain->ops)
-		domain->ops = bus->iommu_ops->default_domain_ops;
+		domain->ops = ops->default_domain_ops;
 
 	if (iommu_is_dma_domain(domain) && iommu_get_dma_cookie(domain)) {
 		iommu_domain_free(domain);
@@ -2120,6 +2122,9 @@ static int iommu_group_do_attach_device(struct device *dev, void *data)
 {
 	struct iommu_domain *domain = data;
 
+	if (dev_iommu_ops(dev) != domain->owner)
+		return -EINVAL;
+
 	return __iommu_attach_device(domain, dev);
 }
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 3589d1b8f922..86fa52025e75 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -95,6 +95,7 @@ struct iommu_domain_geometry {
 struct iommu_domain {
 	unsigned type;
 	const struct iommu_domain_ops *ops;
+	const struct iommu_ops *owner; /* Whose domain_alloc we came from */
 	unsigned long pgsize_bitmap;	/* Bitmap of page sizes in use */
 	struct iommu_domain_geometry geometry;
 	struct iommu_dma_cookie *iova_cookie;
-- 
2.36.1.dirty