[PATCH 3/11] arch/x86/kernel: Correct NULL test

[Julia Lawall]

From: Julia Lawall <ju...@diku.dk>

dev was tested just above, so drop the second test.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@r@
expression *x;
expression e;
identifier l;
@@

if (x == NULL || ...) {
... when forall
return ...; }
... when != goto l;
when != x = e
when != &x
*x == NULL
// </smpl>

Signed-off-by: Julia Lawall <ju...@diku.dk>

---
arch/x86/kernel/amd_iommu.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index adb0ba0..2c4a501 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -118,7 +118,7 @@ static bool check_device(struct device *dev)
return false;

/* No device or no PCI device */
- if (!dev || dev->bus != &pci_bus_type)
+ if (dev->bus != &pci_bus_type)
return false;

devid = get_device_id(dev);
--
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[Ludovic FERRE]

Hello Julia,

May be it would be worthy to take your changes one step further and to
report if the function is called with a null device pointer (which
indicates a problem in the calling code, right?).

Here's a patch moving the null pointer check to its own if block and
reporting the null pointer function call using printk based on
2.6.33-rc6 code.

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 23824fe..1a1d87c 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -114,11 +114,17 @@ static bool check_device(struct device *dev)
{
u16 devid;

- if (!dev || !dev->dma_mask)
+ /* Function is called with a null pointer. Flag this and return false */
+ if (!dev){
+ printk(KERN_INFO "amd_iommu check_device called with a
null pointer device\n");
+ return false;
+ }
+
+ if (!dev->dma_mask)
return false;

/* No device or no PCI device */
- if (!dev || dev->bus != &pci_bus_type)
+ if (dev->bus != &pci_bus_type)
return false;

devid = get_device_id(dev);

--
Ludovic

[Joerg Roedel]

On Sat, Feb 06, 2010 at 09:42:39AM +0100, Julia Lawall wrote:
> From: Julia Lawall <ju...@diku.dk>
>
> dev was tested just above, so drop the second test.

Applied to amd-iommu/fixes. Thanks Julia.

Joerg