[PATCH] x86-64: Calgary IOMMU: deobfuscate calgary_init

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@kudzu.us>
Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 7 insertions, 5 deletions

diff --git a/arch/x86_64/kernel/pci-calgary.c b/arch/x86_64/kernel/pci-calgary.c
index f760045d6d35..1100031528dc 100644
--- a/arch/x86_64/kernel/pci-calgary.c
+++ b/arch/x86_64/kernel/pci-calgary.c
@@ -816,6 +816,8 @@ static int __init calgary_init_one(struct pci_dev *dev)
         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);
@@ -842,10 +844,10 @@ 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);
@@ -861,12 +863,12 @@ 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);
@@ -882,7 +884,7 @@ 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;
 }