Received-SPF: pass (google.com: domain of linux-kernel+bounces-74626-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com,
	Will Deacon <will@kernel.org>,
	iommu@lists.linux.dev,
	Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Petr Tesarik <petr.tesarik1@huawei-partners.com>,
	Dexuan Cui <decui@microsoft.com>,
	Nicolin Chen <nicolinc@nvidia.com>,
	Michael Kelley <mhklinux@outlook.com>
Subject: [PATCH v4 2/5] swiotlb: Enforce page alignment in swiotlb_alloc()
Date: Wed, 21 Feb 2024 11:35:01 +0000
Message-Id: <20240221113504.7161-3-will@kernel.org>
In-Reply-To: <20240221113504.7161-1-will@kernel.org>
References: <20240221113504.7161-1-will@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

When allocating pages from a restricted DMA pool in swiotlb_alloc(),
the buffer address is blindly converted to a 'struct page *' that is
returned to the caller. In the unlikely event of an allocation bug,
page-unaligned addresses are not detected and slots can silently be
double-allocated.

Add a simple check of the buffer alignment in swiotlb_alloc() to make
debugging a little easier if something has gone wonky.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 kernel/dma/swiotlb.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 2ec2cc81f1a2..ab7fbb40bc55 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1643,6 +1643,12 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
 		return NULL;
 
 	tlb_addr = slot_addr(pool->start, index);
+	if (unlikely(!PAGE_ALIGNED(tlb_addr))) {
+		dev_WARN_ONCE(dev, 1, "Cannot allocate pages from non page-aligned swiotlb addr 0x%pa.\n",
+			      &tlb_addr);
+		swiotlb_release_slots(dev, tlb_addr);
+		return NULL;
+	}
 
 	return pfn_to_page(PFN_DOWN(tlb_addr));
 }
-- 
2.44.0.rc0.258.g7320e95886-goog