linux-kernel - [PATCH 2 of 4] x86-64: Calgary IOMMU: deobfuscate calgary

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Message-Id: <e0562474cf16b13d8c3c.1159605810@rhun.haifa.ibm.com>
Date:	Sat, 30 Sep 2006 11:43:30 +0300
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	ak@...e.de
Cc:	jdmason@...zu.us, linux-kernel@...r.kernel.org, discuss@...-64.org,
	muli@...ibm.com
Subject: [PATCH 2 of 4] x86-64: Calgary IOMMU: deobfuscate calgary_init

1 files changed, 7 insertions(+), 5 deletions(-)
arch/x86_64/kernel/pci-calgary.c |   12 +++++++-----


# HG changeset patch
# User Muli Ben-Yehuda <muli@...ibm.com>
# Date 1159604311 -10800
# Node ID e0562474cf16b13d8c3c815fce3159ba7cd0f540
# Parent  28658cf477bc8c6adc5a5335363a4d1428f58273
x86-64: Calgary IOMMU: deobfuscate calgary_init

From: Jon Mason <jdmason@...zu.us>

calgary_init's for loop does not correspond to the actual device being
checked, which makes its upperbound check for array overflow useless.
Changing this to a do-while loop is the correct way of doing this.
There should be no possibility of spinning forever in this loop, as
pci_get_device states that it will go through all iterations, then
return NULL (thus breaking the loop).

Signed-off-by: Jon Mason <jdmason@...zu.us>
Signed-off-by: Muli Ben-Yehuda <muli@...ibm.com>

diff -r 28658cf477bc -r e0562474cf16 arch/x86_64/kernel/pci-calgary.c
--- a/arch/x86_64/kernel/pci-calgary.c	Sat Sep 30 11:16:12 2006 +0300
+++ b/arch/x86_64/kernel/pci-calgary.c	Sat Sep 30 11:18:31 2006 +0300
@@ -817,6 +817,8 @@ static int __init calgary_init_one(struc
 	void __iomem *bbar;
 	int ret;
 
+	BUG_ON(dev->bus->number >= MAX_PHB_BUS_NUM);
+
 	address = locate_register_space(dev);
 	/* map entire 1MB of Calgary config space */
 	bbar = ioremap_nocache(address, 1024 * 1024);
@@ -843,10 +845,10 @@ done:
 
 static int __init calgary_init(void)
 {
-	int i, ret = -ENODEV;
+	int ret = -ENODEV;
 	struct pci_dev *dev = NULL;
 
-	for (i = 0; i < MAX_PHB_BUS_NUM; i++) {
+	do {
 		dev = pci_get_device(PCI_VENDOR_ID_IBM,
 				     PCI_DEVICE_ID_IBM_CALGARY,
 				     dev);
@@ -862,12 +864,12 @@ static int __init calgary_init(void)
 		ret = calgary_init_one(dev);
 		if (ret)
 			goto error;
-	}
+	} while (1);
 
 	return ret;
 
 error:
-	for (i--; i >= 0; i--) {
+	do {
 		dev = pci_find_device_reverse(PCI_VENDOR_ID_IBM,
 					      PCI_DEVICE_ID_IBM_CALGARY,
 					      dev);
@@ -883,7 +885,7 @@ error:
 		calgary_disable_translation(dev);
 		calgary_free_bus(dev);
 		pci_dev_put(dev); /* Undo calgary_init_one()'s pci_dev_get() */
-	}
+	} while (1);
 
 	return ret;
 }
-
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