linux-kernel - [PATCH 4.7 059/143] iommu/io-pgtable-arm-v7s: Fix attributes when splitting blocks

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Date:   Mon,  5 Sep 2016 18:43:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 4.7 059/143] iommu/io-pgtable-arm-v7s: Fix attributes when splitting blocks

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Robin Murphy <robin.murphy@....com>

commit e633fc7a1347528c3b4a6bbdeb41f5d63988242c upstream.

Due to the attribute bits being all over the place in the different
types of short-descriptor PTEs, when remapping an existing entry, e.g.
splitting a section into pages, we take the approach of decomposing
the PTE attributes back to the IOMMU API flags to start from scratch.

On inspection, though, the existing code seems to have got the read-only
bit backwards and ignored the XN bit. How embarrassing...

Fortunately the primary user so far, the Mediatek IOMMU, both never
splits blocks (because it only serves non-overlapping DMA API calls) and
also ignores permissions anyway, but let's put things right before any
future users trip up.

Fixes: e5fc9753b1a8 ("iommu/io-pgtable: Add ARMv7 short descriptor support")
Signed-off-by: Robin Murphy <robin.murphy@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/iommu/io-pgtable-arm-v7s.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -286,12 +286,14 @@ static int arm_v7s_pte_to_prot(arm_v7s_i
 	int prot = IOMMU_READ;
 	arm_v7s_iopte attr = pte >> ARM_V7S_ATTR_SHIFT(lvl);

-	if (attr & ARM_V7S_PTE_AP_RDONLY)
+	if (!(attr & ARM_V7S_PTE_AP_RDONLY))
 		prot |= IOMMU_WRITE;
 	if ((attr & (ARM_V7S_TEX_MASK << ARM_V7S_TEX_SHIFT)) == 0)
 		prot |= IOMMU_MMIO;
 	else if (pte & ARM_V7S_ATTR_C)
 		prot |= IOMMU_CACHE;
+	if (pte & ARM_V7S_ATTR_XN(lvl))
+		prot |= IOMMU_NOEXEC;

 	return prot;
 }