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From: Christoph Hellwig <hch@lst.de>
To: iommu@lists.linux-foundation.org, Russell King <linux@armlinux.org.uk>
Cc: Robin Murphy <robin.murphy@arm.com>, linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] dma-mapping: truncate dma masks to what dma_addr_t can hold
Date: Tue, 21 May 2019 14:47:28 +0200
Message-ID: <20190521124729.23559-2-hch@lst.de> (raw)
In-Reply-To: <20190521124729.23559-1-hch@lst.de>

The dma masks in struct device are always 64-bits wide.  But for builds
using a 32-bit dma_addr_t we need to ensure we don't store an
unsupportable value.  Before Linux 5.0 this was handled at least by
the ARM dma mapping code by never allowing to set a larger dma_mask,
but these days we allow the driver to just set the largest supported
value and never fall back to a smaller one.  Ensure this always works
by truncating the value.

Fixes: 9eb9e96e97b3 ("Documentation/DMA-API-HOWTO: update dma_mask sections")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/dma/mapping.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index f7afdadb6770..1f628e7ac709 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -317,6 +317,12 @@ void arch_dma_set_mask(struct device *dev, u64 mask);
 
 int dma_set_mask(struct device *dev, u64 mask)
 {
+	/*
+	 * Truncate the mask to the actually supported dma_addr_t width to
+	 * avoid generating unsupportable addresses.
+	 */
+	mask = (dma_addr_t)mask;
+
 	if (!dev->dma_mask || !dma_supported(dev, mask))
 		return -EIO;
 
@@ -330,6 +336,12 @@ EXPORT_SYMBOL(dma_set_mask);
 #ifndef CONFIG_ARCH_HAS_DMA_SET_COHERENT_MASK
 int dma_set_coherent_mask(struct device *dev, u64 mask)
 {
+	/*
+	 * Truncate the mask to the actually supported dma_addr_t width to
+	 * avoid generating unsupportable addresses.
+	 */
+	mask = (dma_addr_t)mask;
+
 	if (!dma_supported(dev, mask))
 		return -EIO;
 
-- 
2.20.1

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Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-21 12:47 fixups for the dma_set_mask beahvior change in 5.1 Christoph Hellwig
2019-05-21 12:47 ` Christoph Hellwig [this message]
2019-05-21 13:04   ` [PATCH 1/2] dma-mapping: truncate dma masks to what dma_addr_t can hold Russell King - ARM Linux admin
2019-05-21 13:15     ` Christoph Hellwig
2019-05-29 12:22       ` Christoph Hellwig
2019-06-14  7:46         ` Christoph Hellwig
2019-06-25  5:54           ` Christoph Hellwig
2019-05-21 12:47 ` [PATCH 2/2] ARM: dma-mapping: allow larger DMA mask than supported Christoph Hellwig
2019-05-21 13:00   ` Russell King - ARM Linux admin
2019-05-21 13:04     ` Christoph Hellwig

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