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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Aaron Ma <aaron.ma@canonical.com>,
        Joerg Roedel <jroedel@suse.de>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 099/125] iommu/amd: Fix NULL dereference bug in match_hid_uid
Date:   Wed,  4 Dec 2019 18:56:44 +0100
Message-Id: <20191204175325.116801683@linuxfoundation.org>
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From: Aaron Ma <aaron.ma@canonical.com>

[ Upstream commit bb6bccba390c7d743c1e4427de4ef284c8cc6869 ]

Add a non-NULL check to fix potential NULL pointer dereference
Cleanup code to call function once.

Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Fixes: 2bf9a0a12749b ('iommu/amd: Add iommu support for ACPI HID devices')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/amd_iommu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index e81acb2b6ee7d..c898c70472bb2 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -176,10 +176,14 @@ static struct lock_class_key reserved_rbtree_key;
 static inline int match_hid_uid(struct device *dev,
 				struct acpihid_map_entry *entry)
 {
+	struct acpi_device *adev = ACPI_COMPANION(dev);
 	const char *hid, *uid;
 
-	hid = acpi_device_hid(ACPI_COMPANION(dev));
-	uid = acpi_device_uid(ACPI_COMPANION(dev));
+	if (!adev)
+		return -ENODEV;
+
+	hid = acpi_device_hid(adev);
+	uid = acpi_device_uid(adev);
 
 	if (!hid || !(*hid))
 		return -ENODEV;
-- 
2.20.1