linux-kernel - [PATCH review for 4.4 42/47] iommu/io-pgtable-arm: Check for leaf entry before dereferencing it

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Message-ID: <20170920044445.7392-42-alexander.levin@verizon.com>
Date:   Wed, 20 Sep 2017 04:45:10 +0000
From:   "Levin, Alexander (Sasha Levin)" <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>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH review for 4.4 42/47] iommu/io-pgtable-arm: Check for leaf
 entry before dereferencing it

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

[ Upstream commit ed46e66cc1b3d684042f92dfa2ab15ee917b4cac ]

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.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index dad768caa9c5..18751b1dfd3d 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -335,8 +335,12 @@ static int __arm_lpae_map(struct arm_lpae_io_pgtable *data, unsigned long iova,
 		if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_NS)
 			pte |= ARM_LPAE_PTE_NSTABLE;
 		__arm_lpae_set_pte(ptep, pte, cfg);
-	} else {
+	} else if (!iopte_leaf(pte, lvl)) {
 		cptep = iopte_deref(pte, data);
+	} else {
+		/* We require an unmap first */
+		WARN_ON(!selftest_running);
+		return -EEXIST;
 	}
 
 	/* Rinse, repeat */
-- 
2.11.0