linux-kernel - [PATCH] s390/pci: Fix dev.dma_range

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Message-Id: <20250306-fix_dma_map_alloc-v1-1-b4fa44304eac@linux.ibm.com>
Date: Thu, 06 Mar 2025 16:25:29 +0100
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Matthew Rosato <mjrosato@...ux.ibm.com>, Joerg Roedel <jroedel@...e.de>,
        Will Deacon <will@...nel.org>, Gerd Bayer <gbayer@...ux.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Niklas Schnelle <schnelle@...ux.ibm.com>
Subject: [PATCH] s390/pci: Fix dev.dma_range_map missing sentinel element

The fixed commit sets up dev.dma_range_map but missed that this is
supposed to be an array of struct bus_dma_region with a sentinel element
with the size field set to 0 at the end. This would lead to overruns in
e.g. dma_range_map_min(). It could also result in wrong translations
instead of DMA_MAPPIN_ERROR in translate_phys_to_dma() if the paddr were
to not fit in the aperture. Fix this by using the dma_direct_set_offset()
helper which creates a sentinel for us.

Fixes: d236843a6964 ("s390/pci: store DMA offset in bus_dma_region")
Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
---
This is based on iommu/next which contains the fixed commit
---
 arch/s390/pci/pci_bus.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/arch/s390/pci/pci_bus.c b/arch/s390/pci/pci_bus.c
index 0e725039861f92925a38f7ff7cb6de6b0d965ac3..14310c3b48860a16de13536adf95ef99e6af21cc 100644
--- a/arch/s390/pci/pci_bus.c
+++ b/arch/s390/pci/pci_bus.c
@@ -287,23 +287,21 @@ static struct zpci_bus *zpci_bus_alloc(int topo, bool topo_is_tid)
 static void pci_dma_range_setup(struct pci_dev *pdev)
 {
 	struct zpci_dev *zdev = to_zpci(pdev);
-	struct bus_dma_region *map;
-	u64 aligned_end;
+	u64 aligned_end, size;
+	dma_addr_t dma_start;
+	int ret;
 
-	map = kzalloc(sizeof(*map), GFP_KERNEL);
-	if (!map)
-		return;
-
-	map->cpu_start = 0;
-	map->dma_start = PAGE_ALIGN(zdev->start_dma);
+	dma_start = PAGE_ALIGN(zdev->start_dma);
 	aligned_end = PAGE_ALIGN_DOWN(zdev->end_dma + 1);
-	if (aligned_end >= map->dma_start)
-		map->size = aligned_end - map->dma_start;
+	if (aligned_end >= dma_start)
+		size = aligned_end - dma_start;
 	else
-		map->size = 0;
-	WARN_ON_ONCE(map->size == 0);
+		size = 0;
+	WARN_ON_ONCE(size == 0);
 
-	pdev->dev.dma_range_map = map;
+	ret = dma_direct_set_offset(&pdev->dev, 0, dma_start, size);
+	if (ret)
+		pr_err("Failed to allocate DMA range map for %s\n", pci_name(pdev));
 }
 
 void pcibios_bus_add_device(struct pci_dev *pdev)

---
base-commit: e840414e5a73ac02ffba6299b46f535a0b7cba98
change-id: 20250306-fix_dma_map_alloc-b3b05903dcfb

Best regards,
-- 
Niklas Schnelle