linux-kernel - [PATCH AUTOSEL for 4.9 018/156] iommu/io-pgtable-arm-v7s: Check for leaf entry before dereferencing it

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Message-ID: <20171207154845.4814-18-alexander.levin@verizon.com>
Date:   Thu, 7 Dec 2017 15:48:58 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.9 018/156] iommu/io-pgtable-arm-v7s: Check for
 leaf entry before dereferencing it

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>

[ Upstream commit a03849e7210277fa212779b7cd9c30e1ab6194b2 ]

Do a check for already installed leaf entry at the current level before
dereferencing it in order to avoid walking the page table down with
wrong pointer to the next level.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
CC: Will Deacon <will.deacon@....com>
CC: Robin Murphy <robin.murphy@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/iommu/io-pgtable-arm-v7s.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index f50e51c1a9c8..d68a552cfe8d 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -418,8 +418,12 @@ static int __arm_v7s_map(struct arm_v7s_io_pgtable *data, unsigned long iova,
 			pte |= ARM_V7S_ATTR_NS_TABLE;
 
 		__arm_v7s_set_pte(ptep, pte, 1, cfg);
-	} else {
+	} else if (ARM_V7S_PTE_IS_TABLE(pte, lvl)) {
 		cptep = iopte_deref(pte, lvl);
+	} else {
+		/* We require an unmap first */
+		WARN_ON(!selftest_running);
+		return -EEXIST;
 	}
 
 	/* Rinse, repeat */
-- 
2.11.0