linux-kernel - [PATCH v2] iommu/dma: Fix domain init

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Date: Wed, 29 May 2024 16:54:09 +0100
From: Robin Murphy <robin.murphy@....com>
To: joro@...tes.org
Cc: iommu@...ts.linux.dev,
	will@...nel.org,
	linux-kernel@...r.kernel.org,
	Jon Hunter <jonathanh@...dia.com>,
	Jerry Snitselaar <jsnitsel@...hat.com>
Subject: [PATCH v2] iommu/dma: Fix domain init

Despite carefully rewording the kerneldoc to describe the new direct
interaction with dma_range_map, it seems I managed to confuse myself in
removing the redundant force_aperture check and ended up making the code
not do that at all. This led to dma_range_maps inadvertently being able
to set iovad->start_pfn = 0, and all the nonsensical chaos which ensues
from there. Restore the correct behaviour of constraining base_pfn to
the domain aperture regardless of dma_range_map, and not trying to apply
dma_range_map constraints to the basic IOVA domain since they will be
properly handled with reserved regions later.

Reported-by: Jon Hunter <jonathanh@...dia.com>
Reported-by: Jerry Snitselaar <jsnitsel@...hat.com>
Fixes: ad4750b07d34 ("iommu/dma: Make limit checks self-contained")
Tested-by: Jerry Snitselaar <jsnitsel@...hat.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
Signed-off-by: Robin Murphy <robin.murphy@....com>
---

Since I've now got round to rebasing on -rc1, I figured I may as well
send a v2 with updated tags to avoid any confusion.

 drivers/iommu/dma-iommu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index f731e4b2a417..43520e7275cc 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -686,15 +686,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, struct device *dev
 
 	/* Check the domain allows at least some access to the device... */
 	if (map) {
-		dma_addr_t base = dma_range_map_min(map);
-		if (base > domain->geometry.aperture_end ||
+		if (dma_range_map_min(map) > domain->geometry.aperture_end ||
 		    dma_range_map_max(map) < domain->geometry.aperture_start) {
 			pr_warn("specified DMA range outside IOMMU capability\n");
 			return -EFAULT;
 		}
-		/* ...then finally give it a kicking to make sure it fits */
-		base_pfn = max(base, domain->geometry.aperture_start) >> order;
 	}
+	/* ...then finally give it a kicking to make sure it fits */
+	base_pfn = max_t(unsigned long, base_pfn,
+			 domain->geometry.aperture_start >> order);
 
 	/* start_pfn is always nonzero for an already-initialised domain */
 	mutex_lock(&cookie->mutex);
-- 
2.39.2.101.g768bb238c484.dirty